%I #4 Mar 30 2012 17:33:55
%S 1,256,72057594037927936
%N 2^(2p - 1)/32, where p is a Mersenne prime A000668(n).
%F a(n) = 2^(2*A000668(n)-1)/32 = A139294(n)/32.
%K bref,nonn
%O 1,2
%A _Omar E. Pol_, Apr 13 2008
