In my defence:
I found the first 25,000 primes, not 250,000 primes.
Also, I can't see how it would find pseudo-primes. It is based on the theorem which says that each number which is not a prime, can be factored into primes. Ergo: if a number is divisible by some number (= any non-prime), it is also divisible by some primes.
I looked up pseudo-primes in Wikipedia and that is something completely different. For example, they say that the first pseudo-prime is 341 = 11*31. Pseudo-primes can also be found with this method, because they can be divided by some primes.
(Ok, found 250,000 primes in 73 seconds on 256 MB RAM. And I knew exactly how much memory to set aside )