johngg: Your vector solution works, but it doesn't remember between function calls the primes it's found, and it must be doing something odd, since calling it for a large number like 234223345333 gives the message:

# Assigning to negative offset in vec.
[download]

Calling it for a somewhat smaller number like 234223345 just makes it run practically forever.

EDIT: Never mind, I see the problem. You have to store a bit for each number that could potentially be a prime, so when the max number is extremely large, you apparently go out of bounds. Plus, hits on numbers that have already been punched out increase significantly after the first few primes, and I imagine it would be more efficient to pick some point after which to switch from skip counting to modulo testing.