Hi Kristen1...
Fermat primes are of the form 2^{n}+1. An easy argument shows that n itself must be a power of 2 -- see Fermat number - Wikipedia, the free encyclopedia. So of your choices only 4^{8}+1=2^{16}+1 can possibly be prime, and it is.
Hi Kristen1...
Fermat primes are of the form 2^{n}+1. An easy argument shows that n itself must be a power of 2 -- see Fermat number - Wikipedia, the free encyclopedia. So of your choices only 4^{8}+1=2^{16}+1 can possibly be prime, and it is.