Let an=22n+1a_n = 2^{2^n} + 1an=22n+1 be a Fermat number. What is GCD(an,am)\text{GCD}(a_n, a_m)GCD(an,am) for n≠mn \neq mn=m?
111
222
2n+12^n + 12n+1
amin(n,m)a_{\min(n,m)}amin(n,m)