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%I #6 Jun 06 2017 14:26:11
%S 0,1,2,4,5,6
%N Numbers n such that (3^(2^n) + 1)/2 is prime.
%C See A171381, which is the main entry for this sequence.
%o (PARI) is(n)=ispseudoprime((3^(2^n)+1)/2) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y Cf. A093625, A171381.
%K nonn,more,hard
%O 1,3
%A _N. J. A. Sloane_, Dec 09 2009