This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A101329 #12 Jun 02 2025 00:26:39 %S A101329 7,31,131071, %T A101329 231584178474632390847141970017375815706539969331281128078915168015826259279871 %N A101329 2^(2^(2^x)+1)-1 = M(F(x)) == Mersenne(Fermat(x)). %C A101329 Mersenne-Fermat numbers. %F A101329 a(n) = A070969(2^n)-2. - _R. J. Mathar_, Apr 22 2007 %e A101329 M(F(0))=7 %e A101329 M(F(1))=31 %e A101329 M(F(2))=131071 %e A101329 M(F(3))=231584178474632390847141970017375815706539969331281128078915168015826259279871 %o A101329 (PARI) for(x=0,3,print(2^(2^(2^x)+1)-1)) %K A101329 nonn %O A101329 0,1 %A A101329 _Jorge Coveiro_, Dec 24 2004