my solutions to project euler problems
3.c - 3best.c is much more simple, but I wanted to try my hand at generating primes so I did it the long way
5.c - this is just asking for the least common multiple of 1-20, would be quicker on paper than writing the code
7.c - used sieve of eratosthenes after looking it up. much more refined prime generation than what I use in 3.c