Math Is Fun Forum

LQ

Real Member

Registered: 2006-12-04

Posts: 1,285

Evaluate my primefunction

(1-n)integral(2^n)/2 = p (n>1) & (n != 2q)

(2+4+8)/2 = 7
(2+4+8+16+32)/2 = 31
(2+4+8+16+32+64+128)/2 = 127
(2+4+8+16+32+64+128+256+512)/2 = 511

etc. etc.

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I see clearly now, the universe have the black dots, Thus I am on my way of inventing this remedy...

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Evaluate my primefunction

Hi L.Q.

I am not following you here. Are you saying that your function generates only primes? Because
511= 7*73

Last edited by bobbym (2009-08-15 21:16:36)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Evaluate my primefunction

An easier way of saying that is just 2^n - 1.
It's definitely composite if n is, but even if n is prime we still can't guarantee that the function will be.

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Why did the vector cross the road?
It wanted to be normal.

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Evaluate my primefunction

If

is a prime and

is also prime, then

is called a Mersenne prime and denoted

. Not every number of the form

where

is prime is necessarily prime, mind you – e.g.

.

LQ

Real Member

Registered: 2006-12-04

Posts: 1,285

Re: Evaluate my primefunction

Aah, thanks, you're right sorry for interrupting, yes this must've been in the back of my head why I shared it.

Basically the idea was that a prime P would be as far away from factors as possible, can anyone make a function f that would evaluate that, and I'd be delighted to look on the result. so it has to contain the variable radius r i imagine.

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I see clearly now, the universe have the black dots, Thus I am on my way of inventing this remedy...