SP4421 GF2 - Irreducible polynomials over GF2

Find the number of degree **n** irreducible polynomials over GF(2). For example: for n=1 there are two such polynoms: x and x+1. For **n**=2 there is only one: x $ ^{2} $ +x+1. Note that in R\[x\] the polynom x $ ^{2} $ +1 is irreducible, but not over GF(2), because x $ ^{2} $ +1=(x+1)\*(x+1)

A single positive integer **n**, where **n**

Output the answer for **n.**