Suppose p1, p2, ..., px are all of the primes of the form 3n+1. Let q=p1*p2*...*px. The number 4q^2+3 cannot be divisible by any of p1, p2, ..., px. However, it can only have factors of the form 3n+1. Therefore, there are infinitely many primes of the form 3n+1.
Prime answer
