All of these prime finders are either based on the sieve of 
eratosthenes, or on some other parallel method.  Haven't
quite decided yet.  They are still works in progress, and I 
recommend NOT using any limit generator more than 25.  The upper 
limit of the calculation is 2^n, and I would love getting it to
the point that it could find the primes below 1 billions, but
it's not there yet - requires too much memory.

Thus far have implemented
Ruby
Python
Go
Rust(non-working)

Almost all working code taken from 
http://rosettacode.org/wiki/Sieve_of_Eratosthenes