 Fermat primes are primes of the form
with formula_70 a nonnegative integer.They are named after Pierre de Fermat, who conjectured that all such numbers are prime.The first five of these numbers – 3, 5, 17, 257, and 65,537 – are prime, but formula_242 is composite and so are all other Fermat numbers that have been verified as of 2017.