%I #10 Jul 20 2024 15:09:12
%S 7,31,131071,
%T 231584178474632390847141970017375815706539969331281128078915168015826259279871
%N 2^(2^(2^x)+1)-1 = M(F(x)) == Mersenne(Fermat(x))
%C Mersenne-Fermat numbers.
%F a(n) = A070969(2^n)-2. - _R. J. Mathar_, Apr 22 2007
%e M(F(0))=7
%e M(F(1))=31
%e M(F(2))=131071
%e M(F(3))=231584178474632390847141970017375815706539969331281128078915168015826259279871
%o (PARI) for(x=0,3,print(2^(2^(2^x)+1)-1))
%K nonn
%O 0,1
%A _Jorge Coveiro_, Dec 24 2004