%I

%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