Math Is Fun Forum

wintersolstice

Real Member

Registered: 2009-06-06

Posts: 128

seven and thirteen

7 and 13 are the first two happy primes and 91 (7×13) is also a happy number. this means that 19 is happy, this is the 3rd happy prime!

---

Why did the chicken cross the Mobius Band?
To get to the other ...um...!!!

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,384

Re: seven and thirteen

What are happy primes?

---

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: seven and thirteen

Happy numbers are related to a sequence where each term is determined by the sum of the squares of the previous term's digits. eg.

7
49 (= 7²)
97 (= 4² + 9²)
130
10
1
1
1
...

A happy number is a number that initiates a sequence that goes to 1, like 7 does above.

An unhappy number will instead eventually fall into the following loop:
4, 16, 37, 58, 89, 145, 42, 20, 4...

---

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

DarkLightA

Member

Registered: 2009-05-27

Posts: 16

Re: seven and thirteen

Hmm.. Never heard of this.. Is there a use for this sequence?

RickIsAnIdiot

Member

Registered: 2009-06-13

Posts: 5

Re: seven and thirteen

Happy numbers are related to a sequence where each term is determined by the sum of the squares of the previous term's digits. eg.

7
49 (= 7²)
97 (= 4² + 9²)
130
10
1
1
1
...
For mathsyperson
Quote:

A happy number is a number that initiates a sequence that goes to 1, like 7 does above.

An unhappy number will instead eventually fall into the following loop:
4, 16, 37, 58, 89, 145, 42, 20, 4...

RickIsAnIdiot

Do you have any more Happy Number examples.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: seven and thirteen

Hi Rick;

http://en.wikipedia.org/wiki/Happy_number

---

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.

RickIsAnIdiot

Member

Registered: 2009-06-13

Posts: 5

Re: seven and thirteen

For bobbym
Quote:

http://en.wikipedia.org/wiki/Happy_number

RickIsAnIdiot

Thanks bobbym! keep up the good work..

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: seven and thirteen

Hi Rick;

Please don't be offended but I don't feel comfortable calling anyone an idiot so may I call you Rick. Anyway welcome to the forum.

Last edited by bobbym (2009-06-14 01:43:15)

---

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.

RickyIsAnIdiot

Banned

Registered: 2009-06-15

Posts: 18

Re: seven and thirteen

For bobbym
Quote:
Hi Rick;

Please don't be offended but I don't feel comfortable calling anyone an idiot so may I call you Rick. Anyway welcome to the forum.

RickyIsAnIdiot

That's OK! you can call me Rick,#ick,#rick it's only names? Knowing the meaning's is the main thing...

Last edited by RickyIsAnIdiot (2009-06-16 00:13:47)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: seven and thirteen

That's OK! you can call me Rick,#ick,#rick it's only names? Knowing the meaning's is the main thing...

I don't appreciate what you are trying to do here. The meaning... what are you implying?

Last edited by bobbym (2009-06-16 05:11:49)

---

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.

Kurre

Member

Registered: 2006-07-18

Posts: 280

Re: seven and thirteen

There are two different accounts posting here, both RICKisanidiot and RICKYisanidiot, imo a clear violence to the multiple account rule (which I think exist on this forum?)

RickyIsAnIdiot

Banned

Registered: 2009-06-15

Posts: 18

Re: seven and thirteen

Has Anyone Heard of "DRACULA" Numbers!