Let {fn}n≥0 be the Fibonacci sequence, given by f0=f1=1, and for all positive integers n the recurrence fn+1=fn+fn−1.
Let an=fn+1fn for any non-negative integer n, and let Pn(X)=Xn+an−1Xn−1+...+a1X+a0.
Prove that for all positive integers n≥3 the polynomial Pn(X) is irreducible in Z[X].