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  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

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#3651 Re: This is Cool » ln(x) approximation » 2006-01-10 04:25:30

That's quite an amazing approximation.  Even at values of 100000, it's only ~0.0007 off.

Try to graph

If you can fit that curve to a known and non-log function, you've got an exact approximation.

However, I believe:

Which would just mean that the curve of the difference goes off to infinity.  So I'm thinking either a polynomial or exponential.

#3652 Re: This is Cool » school » 2006-01-10 04:12:41

What's "leet" got to do with this?

Leet as in leet speak, as in slang on the internet, f00.

#3653 Re: Puzzles and Games » Lateral thinking puzzles » 2006-01-09 04:53:46

He was blind and crossing a street.

#3655 Re: Help Me ! » Differentiation » 2006-01-09 03:28:24

Just to clarify:

Now we have:

This isn't exactly clear, so let's write it in a different way:

Or:

Or even:

Is that clearer?

#3656 Re: Help Me ! » Very interesting problems.. » 2006-01-09 03:23:52

O my.. i let my program running all night long but it  crashed at size 43!!!!!! :\\\

Crashed?  What language did you program it in?

I should have size 62 by the next time I post.

#3657 Re: Help Me ! » Differentiation » 2006-01-08 17:48:49

(a / b) / (c / d) = (a / b) * (d / c)

(3 / 2) / (4 / 5) = (3 / 2) * (5 / 4) = 15 / 8

Be careful writing 1/4x.  It looks like (1/4)x, when in reality it's 1 / (4x).

y = 4 + 1/4x = 4 + 4^-1 * x^-1, that 4 is on the bottom as well.  Of course, 4^-1 = 1/4

y = 4 + 1/4 * x^-1

Try doing that.

#3658 Re: Help Me ! » Help with evil complex numbers! » 2006-01-08 11:14:47

The reason why I did that is because x and x*, and z and z*, have a lot of the same terms in them, which you can take advantage of if you put them in full complex form.

From there, it's just plugging them in and trying to solve for c and d.

#3659 Re: Help Me ! » Help with evil complex numbers! » 2006-01-08 07:45:34

First, start by doing a few quick substitutions:

x   = a + bi (where a and b are real)
x* = a - bi

z   = c + di (where c and d are real)
z* = c - di

xx* = (a + bi)(a - bi) = a^2 + b^2
z - z* = c + di - (c - di) = 2di

So:

a^2 + b^2 + 3(2di) = 13 + 12i

Since i is the only possible imaginary value (all other variables must be real):

a^2 + b^2 = 13 and 6di = 12i

di = 2i, and since d must be real, d = 2

So z = c + 2i, where c is any real number.  The simpilest solution is z = 2i (c = 0)

#3660 Re: Puzzles and Games » Lateral thinking puzzles » 2006-01-07 13:48:16

Mr. Theft just likes to buy a lot of shoes from that one store.

Please give the other two clues.

#3661 Re: Help Me ! » Very interesting problems.. » 2006-01-07 11:11:34

Here are the solutions from size 32 to 35, they seem to increase as the size does.  Also note that each solution appears twice, once forward and once in the reverse order.

Size: 32
1 8 28 21 4 32 17 19 30 6 3 13 12 24 25 11 5 31 18 7 29 20 16 9 27 22 14 2 23 26 10 15
Size: 32
1 15 10 26 23 2 14 22 27 9 16 20 29 7 18 31 5 11 25 24 12 13 3 6 30 19 17 32 4 21 28 8
Size: 33
1 8 28 21 4 32 17 19 30 6 3 13 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 14 2 23 26 10 15
Size: 33
1 15 10 26 23 2 14 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 13 3 6 30 19 17 32 4 21 28 8
Size: 34
1 3 13 12 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 14 22 27 9 16 33 31 18 7 29 20 5 11 25 24
Size: 34
1 3 13 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 14 2 23 26 10 15 34 30 6 19 17 32 4 21 28 8
Size: 34
1 3 13 12 24 25 11 14 22 27 9 16 33 31 18 7 29 20 5 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 34
1 3 13 12 24 25 11 14 22 27 9 16 33 31 18 7 29 20 5 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 34
1 3 13 23 26 10 6 19 30 34 2 14 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 4 32 17 8 28 21 15
Size: 34
1 3 13 23 26 10 6 30 19 17 32 4 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 14 2 34 15 21 28 8
Size: 34
1 3 22 27 9 16 33 31 18 7 29 20 5 4 32 17 19 6 30 34 2 14 11 25 24 12 13 23 26 10 15 21 28 8
Size: 34
1 3 22 27 9 16 33 31 18 7 29 20 5 4 32 17 19 30 6 10 26 23 13 12 24 25 11 14 2 34 15 21 28 8
Size: 34
1 3 33 31 18 7 29 20 16 9 27 22 14 2 34 30 6 19 17 32 4 5 11 25 24 12 13 23 26 10 15 21 28 8
Size: 34
1 3 33 31 18 7 29 20 16 9 27 22 14 2 34 30 19 6 10 26 23 13 12 24 25 11 5 4 32 17 8 28 21 15
Size: 34
1 8 28 21 4 32 17 19 6 30 34 15 10 26 23 2 14 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 13 3
Size: 34
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 5 20 29 7 18 31 33 16 9 27 22 14 11 25 24 12 13 3
Size: 34
1 8 28 21 15 10 26 23 13 12 24 25 11 5 4 32 17 19 6 30 34 2 14 22 27 9 16 20 29 7 18 31 33 3
Size: 34
1 8 28 21 15 10 26 23 13 12 24 25 11 14 2 34 30 6 19 17 32 4 5 20 29 7 18 31 33 16 9 27 22 3
Size: 34
1 8 28 21 15 34 2 14 11 25 24 12 13 23 26 10 6 30 19 17 32 4 5 20 29 7 18 31 33 16 9 27 22 3
Size: 34
1 8 28 21 15 34 2 14 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 4 32 17 19 30 6 10 26 23 13 3
Size: 34
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 5 20 29 7 18 31 33 16 9 27 22 14 11 25 24 12 13 3
Size: 34
1 8 28 21 15 34 30 19 17 32 4 12 13 3 6 10 26 23 2 14 22 27 9 16 33 31 18 7 29 20 5 11 25 24
Size: 34
1 15 21 28 8 17 32 4 5 11 25 24 12 13 23 26 10 6 19 30 34 2 14 22 27 9 16 20 29 7 18 31 33 3
Size: 34
1 15 21 28 8 17 32 4 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 14 2 34 30 19 6 10 26 23 13 3
Size: 34
1 24 25 11 5 20 29 7 18 31 33 16 9 27 22 14 2 23 26 10 6 3 13 12 4 32 17 19 30 34 15 21 28 8
Size: 34
1 24 25 11 5 20 29 7 18 31 33 16 9 27 22 14 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 12 13 3
Size: 35
1 3 6 19 30 34 2 7 18 31 33 16 9 27 22 14 11 25 24 12 13 23 26 10 15 21 28 8 17 32 4 5 20 29 35
Size: 35
1 3 13 12 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 7 18 31 33 16 9 27 22 14 35 29 20 5 11 25 24
Size: 35
1 3 13 12 24 25 11 5 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 14 22 27 9 7 18 31 33 16 20 29 35
Size: 35
1 3 13 12 24 25 11 5 20 29 35 14 22 27 9 16 33 31 18 7 2 23 26 10 15 34 30 6 19 17 32 4 21 28 8
Size: 35
1 3 13 12 24 25 11 14 22 27 9 16 33 31 18 7 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 5 20 29 35
Size: 35
1 3 13 23 26 10 6 19 30 34 2 7 18 31 33 16 9 27 22 14 35 29 20 5 11 25 24 12 4 32 17 8 28 21 15
Size: 35
1 3 13 23 26 10 6 30 19 17 32 4 12 24 25 11 5 20 29 35 14 22 27 9 16 33 31 18 7 2 34 15 21 28 8
Size: 35
1 3 22 27 9 7 18 31 33 16 20 29 35 14 2 34 30 6 19 17 32 4 5 11 25 24 12 13 23 26 10 15 21 28 8
Size: 35
1 3 22 27 9 7 18 31 33 16 20 29 35 14 2 34 30 19 6 10 26 23 13 12 24 25 11 5 4 32 17 8 28 21 15
Size: 35
1 3 22 27 9 16 33 31 18 7 2 14 11 25 24 12 13 23 26 10 6 19 30 34 15 21 28 8 17 32 4 5 20 29 35
Size: 35
1 3 22 27 9 16 33 31 18 7 2 14 35 29 20 5 11 25 24 12 13 23 26 10 15 34 30 6 19 17 32 4 21 28 8
Size: 35
1 3 22 27 9 16 33 31 18 7 2 34 30 6 19 17 32 4 5 20 29 35 14 11 25 24 12 13 23 26 10 15 21 28 8
Size: 35
1 3 22 27 9 16 33 31 18 7 2 34 30 19 6 10 26 23 13 12 24 25 11 14 35 29 20 5 4 32 17 8 28 21 15
Size: 35
1 8 28 21 4 32 17 19 6 30 34 2 14 35 29 7 18 31 33 3 22 27 9 16 20 5 11 25 24 12 13 23 26 10 15
Size: 35
1 8 28 21 4 32 17 19 6 30 34 2 14 35 29 20 16 33 3 22 27 9 7 18 31 5 11 25 24 12 13 23 26 10 15
Size: 35
1 8 28 21 4 32 17 19 6 30 34 15 10 26 23 2 7 18 31 33 16 9 27 22 14 35 29 20 5 11 25 24 12 13 3
Size: 35
1 8 28 21 4 32 17 19 6 30 34 15 10 26 23 2 14 22 27 9 7 18 31 5 11 25 24 12 13 3 33 16 20 29 35
Size: 35
1 8 28 21 4 32 17 19 6 30 34 15 10 26 23 2 14 22 27 9 16 20 5 11 25 24 12 13 3 33 31 18 7 29 35
Size: 35
1 8 28 21 4 32 17 19 6 30 34 15 10 26 23 13 12 24 25 11 5 20 29 35 14 2 7 18 31 33 16 9 27 22 3
Size: 35
1 8 28 21 4 32 17 19 30 6 3 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 13 23 26 10 15 34 2 14 35
Size: 35
1 8 28 21 4 32 17 19 30 6 3 33 16 9 27 22 14 11 25 24 12 13 23 26 10 15 34 2 7 18 31 5 20 29 35
Size: 35
1 8 28 21 4 32 17 19 30 6 10 26 23 13 12 24 25 11 5 20 16 9 27 22 3 33 31 18 7 29 35 14 2 34 15
Size: 35
1 8 28 21 4 32 17 19 30 6 10 26 23 13 12 24 25 11 5 31 18 7 9 27 22 3 33 16 20 29 35 14 2 34 15
Size: 35
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 5 11 25 24 12 13 3 33 31 18 7 29 20 16 9 27 22 14 35
Size: 35
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 5 20 16 9 27 22 14 11 25 24 12 13 3 33 31 18 7 29 35
Size: 35
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 5 20 29 7 18 31 33 16 9 27 22 3 13 12 24 25 11 14 35
Size: 35
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 5 31 18 7 9 27 22 14 11 25 24 12 13 3 33 16 20 29 35
Size: 35
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 12 13 3 33 16 20 29 35 14 22 27 9 7 18 31 5 11 25 24
Size: 35
1 8 28 21 15 10 26 23 2 34 30 6 19 17 32 4 12 13 3 33 31 18 7 29 35 14 22 27 9 16 20 5 11 25 24
Size: 35
1 8 28 21 15 10 26 23 13 3 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 4 32 17 19 6 30 34 2 14 35
Size: 35
1 8 28 21 15 10 26 23 13 3 33 16 9 27 22 14 11 25 24 12 4 32 17 19 6 30 34 2 7 18 31 5 20 29 35
Size: 35
1 8 28 21 15 10 26 23 13 12 4 32 17 19 6 30 34 2 14 35 29 7 18 31 33 3 22 27 9 16 20 5 11 25 24
Size: 35
1 8 28 21 15 10 26 23 13 12 4 32 17 19 6 30 34 2 14 35 29 20 16 33 3 22 27 9 7 18 31 5 11 25 24
Size: 35
1 8 28 21 15 10 26 23 13 12 24 25 11 5 4 32 17 19 6 30 34 2 14 35 29 20 16 33 31 18 7 9 27 22 3
Size: 35
1 8 28 21 15 10 26 23 13 12 24 25 11 14 2 34 30 6 19 17 32 4 5 20 16 9 27 22 3 33 31 18 7 29 35
Size: 35
1 8 28 21 15 10 26 23 13 12 24 25 11 14 2 34 30 6 19 17 32 4 5 31 18 7 9 27 22 3 33 16 20 29 35
Size: 35
1 8 28 21 15 10 26 23 13 12 24 25 11 14 35 29 20 5 4 32 17 19 6 30 34 2 7 18 31 33 16 9 27 22 3
Size: 35
1 8 28 21 15 34 2 7 18 31 33 16 9 27 22 14 35 29 20 5 11 25 24 12 4 32 17 19 30 6 10 26 23 13 3
Size: 35
1 8 28 21 15 34 2 14 11 25 24 12 13 23 26 10 6 30 19 17 32 4 5 20 16 9 27 22 3 33 31 18 7 29 35
Size: 35
1 8 28 21 15 34 2 14 11 25 24 12 13 23 26 10 6 30 19 17 32 4 5 31 18 7 9 27 22 3 33 16 20 29 35
Size: 35
1 8 28 21 15 34 2 14 22 27 9 7 18 31 5 11 25 24 12 4 32 17 19 30 6 10 26 23 13 3 33 16 20 29 35
Size: 35
1 8 28 21 15 34 2 14 22 27 9 16 20 5 11 25 24 12 4 32 17 19 30 6 10 26 23 13 3 33 31 18 7 29 35
Size: 35
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 5 11 25 24 12 13 3 33 31 18 7 29 20 16 9 27 22 14 35
Size: 35
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 5 20 16 9 27 22 14 11 25 24 12 13 3 33 31 18 7 29 35
Size: 35
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 5 20 29 7 18 31 33 16 9 27 22 3 13 12 24 25 11 14 35
Size: 35
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 5 31 18 7 9 27 22 14 11 25 24 12 13 3 33 16 20 29 35
Size: 35
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 12 13 3 33 16 20 29 35 14 22 27 9 7 18 31 5 11 25 24
Size: 35
1 8 28 21 15 34 2 23 26 10 6 30 19 17 32 4 12 13 3 33 31 18 7 29 35 14 22 27 9 16 20 5 11 25 24
Size: 35
1 8 28 21 15 34 30 19 17 32 4 5 11 25 24 12 13 3 6 10 26 23 2 14 22 27 9 7 18 31 33 16 20 29 35
Size: 35
1 8 28 21 15 34 30 19 17 32 4 5 11 25 24 12 13 23 26 10 6 3 33 31 18 7 2 14 22 27 9 16 20 29 35
Size: 35
1 8 28 21 15 34 30 19 17 32 4 12 13 3 6 10 26 23 2 7 18 31 33 16 9 27 22 14 35 29 20 5 11 25 24
Size: 35
1 8 28 21 15 34 30 19 17 32 4 12 13 23 26 10 6 3 22 27 9 16 33 31 18 7 2 14 35 29 20 5 11 25 24
Size: 35
1 15 10 26 23 13 12 24 25 11 5 20 16 9 27 22 3 33 31 18 7 29 35 14 2 34 30 6 19 17 32 4 21 28 8
Size: 35
1 15 10 26 23 13 12 24 25 11 5 31 18 7 9 27 22 3 33 16 20 29 35 14 2 34 30 6 19 17 32 4 21 28 8
Size: 35
1 15 21 28 8 17 32 4 5 11 25 24 12 13 23 26 10 6 19 30 34 2 14 35 29 20 16 33 31 18 7 9 27 22 3
Size: 35
1 15 21 28 8 17 32 4 5 20 29 35 14 11 25 24 12 13 23 26 10 6 19 30 34 2 7 18 31 33 16 9 27 22 3
Size: 35
1 15 21 28 8 17 32 4 12 13 23 26 10 6 19 30 34 2 14 35 29 7 18 31 33 3 22 27 9 16 20 5 11 25 24
Size: 35
1 15 21 28 8 17 32 4 12 13 23 26 10 6 19 30 34 2 14 35 29 20 16 33 3 22 27 9 7 18 31 5 11 25 24
Size: 35
1 15 21 28 8 17 32 4 12 24 25 11 5 20 16 9 27 22 14 2 34 30 19 6 10 26 23 13 3 33 31 18 7 29 35
Size: 35
1 15 21 28 8 17 32 4 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 3 13 23 26 10 6 19 30 34 2 14 35
Size: 35
1 15 21 28 8 17 32 4 12 24 25 11 5 20 29 35 14 22 27 9 16 33 31 18 7 2 34 30 19 6 10 26 23 13 3
Size: 35
1 15 21 28 8 17 32 4 12 24 25 11 5 31 18 7 9 27 22 14 2 34 30 19 6 10 26 23 13 3 33 16 20 29 35
Size: 35
1 15 21 28 8 17 32 4 12 24 25 11 14 22 27 9 16 33 3 13 23 26 10 6 19 30 34 2 7 18 31 5 20 29 35
Size: 35
1 15 34 2 14 35 29 7 18 31 33 3 22 27 9 16 20 5 11 25 24 12 13 23 26 10 6 30 19 17 32 4 21 28 8
Size: 35
1 15 34 2 14 35 29 20 16 33 3 22 27 9 7 18 31 5 11 25 24 12 13 23 26 10 6 30 19 17 32 4 21 28 8
Size: 35
1 24 25 11 5 20 16 9 27 22 3 33 31 18 7 29 35 14 2 34 30 6 19 17 32 4 12 13 23 26 10 15 21 28 8
Size: 35
1 24 25 11 5 20 16 9 27 22 3 33 31 18 7 29 35 14 2 34 30 19 6 10 26 23 13 12 4 32 17 8 28 21 15
Size: 35
1 24 25 11 5 20 16 9 27 22 14 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 12 13 3 33 31 18 7 29 35
Size: 35
1 24 25 11 5 20 16 9 27 22 14 35 29 7 18 31 33 3 13 12 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 35
1 24 25 11 5 20 16 9 27 22 14 35 29 7 18 31 33 3 13 12 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 35
1 24 25 11 5 20 29 7 18 31 33 16 9 27 22 3 13 12 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 14 35
Size: 35
1 24 25 11 5 20 29 35 14 2 7 18 31 33 16 9 27 22 3 6 10 26 23 13 12 4 32 17 19 30 34 15 21 28 8
Size: 35
1 24 25 11 5 20 29 35 14 22 27 9 16 33 31 18 7 2 23 26 10 6 3 13 12 4 32 17 19 30 34 15 21 28 8
Size: 35
1 24 25 11 5 20 29 35 14 22 27 9 16 33 31 18 7 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 12 13 3
Size: 35
1 24 25 11 5 31 18 7 9 27 22 3 33 16 20 29 35 14 2 34 30 6 19 17 32 4 12 13 23 26 10 15 21 28 8
Size: 35
1 24 25 11 5 31 18 7 9 27 22 3 33 16 20 29 35 14 2 34 30 19 6 10 26 23 13 12 4 32 17 8 28 21 15
Size: 35
1 24 25 11 5 31 18 7 9 27 22 14 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 12 13 3 33 16 20 29 35
Size: 35
1 24 25 11 5 31 18 7 9 27 22 14 35 29 20 16 33 3 13 12 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 35
1 24 25 11 5 31 18 7 9 27 22 14 35 29 20 16 33 3 13 12 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 35
1 24 25 11 14 22 27 9 16 33 3 13 12 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 7 18 31 5 20 29 35
Size: 35
1 35 14 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 12 13 3 22 27 9 16 33 31 18 7 29 20 5 11 25 24
Size: 35
1 35 14 2 34 15 10 26 23 13 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 3 6 30 19 17 32 4 21 28 8
Size: 35
1 35 14 2 34 30 6 19 17 32 4 12 24 25 11 5 20 29 7 18 31 33 16 9 27 22 3 13 23 26 10 15 21 28 8
Size: 35
1 35 14 2 34 30 19 6 10 26 23 13 3 22 27 9 16 33 31 18 7 29 20 5 11 25 24 12 4 32 17 8 28 21 15
Size: 35
1 35 14 11 25 24 12 13 3 22 27 9 16 33 31 18 7 29 20 5 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 35
1 35 14 11 25 24 12 13 3 22 27 9 16 33 31 18 7 29 20 5 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 35
1 35 14 22 27 9 16 20 29 7 18 31 33 3 13 12 24 25 11 5 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 35
1 35 14 22 27 9 16 20 29 7 18 31 33 3 13 12 24 25 11 5 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 35
1 35 29 7 18 31 33 3 13 12 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 14 22 27 9 16 20 5 11 25 24
Size: 35
1 35 29 7 18 31 33 3 13 12 24 25 11 5 20 16 9 27 22 14 2 23 26 10 15 34 30 6 19 17 32 4 21 28 8
Size: 35
1 35 29 7 18 31 33 3 13 12 24 25 11 14 22 27 9 16 20 5 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 35
1 35 29 7 18 31 33 3 13 12 24 25 11 14 22 27 9 16 20 5 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 35
1 35 29 7 18 31 33 3 13 23 26 10 6 19 30 34 2 14 22 27 9 16 20 5 11 25 24 12 4 32 17 8 28 21 15
Size: 35
1 35 29 7 18 31 33 3 13 23 26 10 6 30 19 17 32 4 12 24 25 11 5 20 16 9 27 22 14 2 34 15 21 28 8
Size: 35
1 35 29 7 18 31 33 3 22 27 9 16 20 5 4 32 17 19 6 30 34 2 14 11 25 24 12 13 23 26 10 15 21 28 8
Size: 35
1 35 29 7 18 31 33 3 22 27 9 16 20 5 4 32 17 19 30 6 10 26 23 13 12 24 25 11 14 2 34 15 21 28 8
Size: 35
1 35 29 20 5 4 32 17 8 28 21 15 10 26 23 13 12 24 25 11 14 22 27 9 16 33 31 18 7 2 34 30 19 6 3
Size: 35
1 35 29 20 5 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 7 18 31 33 16 9 27 22 14 11 25 24 12 13 3
Size: 35
1 35 29 20 5 4 32 17 8 28 21 15 34 30 19 6 10 26 23 13 12 24 25 11 14 2 7 18 31 33 16 9 27 22 3
Size: 35
1 35 29 20 5 31 18 7 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 12 13 3 33 16 9 27 22 14 11 25 24
Size: 35
1 35 29 20 5 31 18 7 2 34 15 10 26 23 13 12 24 25 11 14 22 27 9 16 33 3 6 30 19 17 32 4 21 28 8
Size: 35
1 35 29 20 5 31 18 7 2 34 30 6 19 17 32 4 12 24 25 11 14 22 27 9 16 33 3 13 23 26 10 15 21 28 8
Size: 35
1 35 29 20 5 31 18 7 2 34 30 19 6 10 26 23 13 3 33 16 9 27 22 14 11 25 24 12 4 32 17 8 28 21 15
Size: 35
1 35 29 20 16 9 27 22 14 2 7 18 31 33 3 6 10 26 23 13 12 24 25 11 5 4 32 17 19 30 34 15 21 28 8
Size: 35
1 35 29 20 16 33 3 13 12 4 32 17 8 28 21 15 34 30 19 6 10 26 23 2 14 22 27 9 7 18 31 5 11 25 24
Size: 35
1 35 29 20 16 33 3 13 12 24 25 11 5 31 18 7 9 27 22 14 2 23 26 10 15 34 30 6 19 17 32 4 21 28 8
Size: 35
1 35 29 20 16 33 3 13 12 24 25 11 14 22 27 9 7 18 31 5 4 32 17 19 6 30 34 2 23 26 10 15 21 28 8
Size: 35
1 35 29 20 16 33 3 13 12 24 25 11 14 22 27 9 7 18 31 5 4 32 17 19 30 6 10 26 23 2 34 15 21 28 8
Size: 35
1 35 29 20 16 33 3 13 23 26 10 6 19 30 34 2 14 22 27 9 7 18 31 5 11 25 24 12 4 32 17 8 28 21 15
Size: 35
1 35 29 20 16 33 3 13 23 26 10 6 30 19 17 32 4 12 24 25 11 5 31 18 7 9 27 22 14 2 34 15 21 28 8
Size: 35
1 35 29 20 16 33 3 22 27 9 7 18 31 5 4 32 17 19 6 30 34 2 14 11 25 24 12 13 23 26 10 15 21 28 8
Size: 35
1 35 29 20 16 33 3 22 27 9 7 18 31 5 4 32 17 19 30 6 10 26 23 13 12 24 25 11 14 2 34 15 21 28 8
Size: 35
1 35 29 20 16 33 31 18 7 9 27 22 14 2 23 26 10 6 3 13 12 24 25 11 5 4 32 17 19 30 34 15 21 28 8
Size: 35
1 35 29 20 16 33 31 18 7 9 27 22 14 2 23 26 10 6 19 30 34 15 21 28 8 17 32 4 5 11 25 24 12 13 3

#3662 Re: Help Me ! » Very interesting problems.. » 2006-01-07 08:07:01

Oh, and as a note, for each combination it will find two lists.  For example, it will find:

Size: 32
1 8 28 21 4 32 17 19 30 6 3 13 12 24 25 11 5 31 18 7 29 20 16 9 27 22 14 2 23 26 10 15
Size: 32
1 15 10 26 23 2 14 22 27 9 16 20 29 7 18 31 5 11 25 24 12 13 3 6 30 19 17 32 4 21 28 8

Which are really the same lists, just in reverse order.  Since it is a circle, order doesn't matter.

#3663 Re: Help Me ! » Very interesting problems.. » 2006-01-07 08:03:13

C++ code:

#include <iostream>
#include <fstream>
#include <vector>
#include <math.h>
#include <windows.h>

using namespace std;

void testVals(vector<int> base, vector<bool> use, vector<int> test);
bool compare(int x, int y);

int main()
{
    int start = GetTickCount();
    for (int size = 2; size <= 32; size++)
    {
        cout << "Testing list size " << size << "..." << endl;
        vector<int> base;
        vector<bool> used;
        vector<int> test;
        for (int gen = 1; gen <= size; gen++)
        {
            base.push_back(gen);
            used.push_back(false);
        }
        testVals(base, used, test);
    }
    int end = GetTickCount();
    cout << "Time: " << (end - start) / 1000.0 << endl;
    return 0;
}

void testVals(vector<int> base, vector<bool> used, vector<int> test) {
    if (test.size() == base.size())
    {
        bool result = compare(test[test.size()-1], test[0]);
        if (result)
        {
            ofstream o("asdf.txt", ios::app);
            o << "Size: " << test.size() << endl;
            for (int x = 0; x < test.size(); x++)
            {
                o << test[x] << " ";
            }
            o << endl;
        }
        return;
    }

    for (int x = 0; x < used.size(); x++)
    {
        if (used[x] == false)
        {
            if (x != 0)
            {
                if (!compare(test[test.size()-1], base[x])) {
                    continue;
                }
            }
            used[x] = true;
            test.push_back(base[x]);
            testVals(base, used, test);
            test.erase(test.end()-1);
            used[x] = false;
        }
    }
}

bool compare(int x, int y)
{
    double temp = sqrt((double)x + y);
    const double amount = 0.00001;
    if (temp + amount > (int) temp && temp - amount < (int)temp)
    {
        return true;
    }
    return false;
}

#3664 Re: Help Me ! » Very interesting problems.. » 2006-01-07 07:58:37

Alright, here is the psuedo code:

Declare three arrays: base (integer), used (boolean), and test (integer)

main:

From size = 2 to size = 32 (or whatever numbers you wan't)
   clear all three lists so they have 0 elements
   From gen = 1 to gen = size
      add gen to base
      add false to used
   testVals(base, used, test)

testVals: recieves arrays base (integer), used (boolean), test (integer)

if test size is equal to base size
   test the list to make sure all adjacent values are perfect squares, then output if they are
   return (exit the function)
else
   From x = 0 to x = size of used
      if used[x] == false //you have yet to use this number in the list
         if x != 0 //don't compare 0 because 0 - 1 is not in the array
            if compare(test[x], test[x-1]) is false // see function compare below
               continue //skip all the code below, but continue in the current loop
      used[x] = true
      add base[x] to the back of test
      testVals(base, used, test)
      remove the last element of test
      used[x] = false

compare: recieves x (int), y (int)

if the sqrt of x + y is an integer
   return true
return false

#3665 Re: This is Cool » So did you hear they found a new prime number? » 2006-01-07 07:47:52

Well since we know there are an infinite amount of primes, this isn't such a great discovery.

However, if we could find an algorithm to find every prime, it would be a great accomplishment.  And the more primes we know, the easier it is to do this.  Especially if we know the really high ones.

#3666 Re: Help Me ! » Very interesting problems.. » 2006-01-07 06:53:53

Hah!  I am so stupid...

The way my algorithm works is that it builds a list of numbers, then tests them.  I completely forgot that I could test them while building, and stop building them if I run into a combination that doesn't work!

My program tried all possible combinations from lists of size 2 to 32 in 0.82 seconds, and found the one at 32.

#3667 Re: Help Me ! » Very interesting problems.. » 2006-01-07 06:41:31

I'm doing the same Krassi.  I had it done before, but I realized that a method I used to cut down on execution time just eliminated some needed tests.  So I'm back to my original program.  It takes O(n!) time, right now it's on size 12 and has to do 479,001,600 comparisons.

#3668 Re: Help Me ! » Sets (Subsets and Proper Subsets) » 2006-01-07 06:36:38

Set A is a subset of set B if for every element in A, that element exists in B.
Set A is a proper subset of set B if A is a subset of B, but B is not a subset of A.

So {Fred, Ashraf} is a subset of S because both Fred and Ashraf  are in S.
But S is not a subset of {Fred, Ashraf} because Sue is not in {Fred, Ashraf}

Now take it one step further:

Prove that if A is a proper subset of B, then A is a subset of B.

Proof: For A to be a proper subset of B, A must be a subset of B.

Therefore A is a subset of B.  QED.

#3669 Re: Help Me ! » Differentiation » 2006-01-06 16:37:53

Nope, you're just plugging in wrong.

-x^-2 = -1 / x^2

So if x = 1/2:

-1 / (1/2)^2 = -1 / (1 / 4) = -4

#3670 Re: Jokes » Why is six afraid of seven? » 2006-01-06 04:50:27

6 saw the movie Se7en.  That would be enough for me.

#3671 Re: Jokes » joke about pi » 2006-01-06 04:47:10

pwnd should be pronounced owned, just like you don't say, "one thousand three hundred and thirty seven" (1337), you just say leet.

And no, there have been no languages which have no pronunciation because language came first, writing came second.

#3673 Re: Help Me ! » integral surface 2.. » 2006-01-06 04:35:13

If x = -1, then:

y = 1 / (1 - 1) = 1 / 0

This is not 0, it is undefined.  In this particular equation, it is either negative or positive infinity.

You're just unlucky with the coordinates you picked to graph it. 

Try x =

1/4 - 1
1/2 - 1
1    - 1
2    - 1
4    - 1
8    - 1

Do the same for the negative side.

#3674 Re: Help Me ! » calculating interest » 2006-01-06 04:29:15

y' = 0.11y, where y' is the amount you get per year, y is the amount you have, and t is time (in years)
dy/y = 0.11dt
ln(|y|) = 0.11t + C
y = C*e^(0.11t)

y(0) = 3,415,569

y(0) = C*e^0
C = 3,415,569

y = 3,415,569*e^(0.11t) --> This is the equation you're looking for

y = 5,000,000
5,000,000 = 3,415,569*e^(0.11t)
e^(0.11t) = 1.464
0.11t = 0.381

t = 3.464

If you don't know calculus, don't worry about the above.  If you do, just ask and I'll explain all the steps.

Edit:

Or are you saying that the interest rate is compounded daily?  I'm having a little trouble understanding your wording.

#3675 Re: Help Me ! » Differentiation » 2006-01-04 16:12:39

Yes, but it is normally stated in a different way, and thus involving less theorms.

y = a * f(x), y' = a * f'(x)

So:

y = 3 * (x^4), where f(x)=x^4
y' = 3 * (4x^3) = 12x^3

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