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%I #9 Jul 23 2017 21:53:26
%S 2,5,17,257,65537
%N Prime numbers of the form 4^k + 1.
%C Similar to Fermat primes, A019434, a(n) is of the form (2^2)^k + 1.
%t Select[4^Range[0, 100] + 1, PrimeQ]
%Y Cf. A019434, A092506.
%K nonn,more
%O 1,1
%A _Robert Price_, Jul 23 2017