Ulam's spiral

[Marmilo]

There was a mathematian called Ulam, and he discovered that if you write out numbers on a square spiral like this (or bigger):

4 3 2
5 0 1
7 8 9

now you leave only prime numbers

3 2
5
7

now replace them with something like an asterisk

* *
*
*
So, I wrote a c++ program that generates them. For a square of size 8, it looks like this:

* *
*
* * *
* * * * *
*
* *
* *
* *

You can see some lines forming now

And after figuring out how to zoom out the terminal I can do this:

that's 300x300 tiles.
What do you guys think?

 

[The epic chicken]

Pretty cool

 

[Marmilo]

Huh, my spaces got deleted. Rip

 

[Marmilo]

This is how it should look:

 

[Altaïr]

Oh, the Ulam spiral, interesting. Just to be curious, did you try to run your program for a larger square size? But I suppose the resources needed become prohibitive at some point. How do you determine if a number is a prime number? The sieve of Eratosthenes I suppose?

 

[Marmilo]

Oh, the Ulam spiral, interesting. Just to be curious, did you try to run your program for a larger square size? But I suppose the resources needed become prohibitive at some point. How do you determine if a number is a prime number? The sieve of Eratosthenes I suppose?

Yup, Erastothenes' sieve. Maximum size I tried was 330 i believe.