What a Proof Is · Challenge problem

A proof uses the factorisation $n^4 + n^2 + 1 = (n^2 + n + 1)(n^2 - n + 1)$ to conclude that $n^4 + n^2 + 1$ is never prime. Reading carefully, for how many integers $n$ with $-10 \le n \le 10$ IS $n^4 + n^2 + 1$ prime?