I am theory lamer, but according to wikipedia:
>Let n ≥ 3 be a positive odd integer. Then n is a Fermat prime if and only if for every a >coprime to n, a is a primitive root mod n if and only if a is a quadratic nonresidue mod >n.
Looks like sqrt(2) is not primitive root, so showing that it is nonresidue shows compositeness of Fn ?
The original program computes sq2a^2 = 2+sqrt(2)=sqrt(2)*(1+sqrt(2)) (at least in C)
so showing that any of sqrt(2),1+sqrt(2),1sqrt(2) is nonresidue shows compositeness of Fn?
The above reasoning may be quite buggy :)
