Sieve of Atkins ported from http://compoasso.free.fr/primelistweb/ressource/Atkin3.java
It is a large improvement on the other sieve you've probably heard of, "Sieve of Eratosthenes".
Solves project euler #7 on a 2013 MacBook Pro in :
0.77s user 0.04s system 83% cpu 0.969 total