The number $n^4 + 4$ is never prime for $n>1$ I am taking a basic algebra course, and one of the proposed problems asks to prove that  $n^4 + 4$ is never a prime number for $n>1$.
I am able to prove it in some particular cases, but I am not able to do it when $n$ is an odd multiple of $5$.   

$n^4 + 4 = (2 - 2 n + n^2) (2 + 2 n + n^2)$
