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 A336117 #16 Jul 11 2020 10:19:38 %S A336117 7,13,29,97,113,193,449,509,769,7937,12289,114689,520193,786433, %T A336117 7340033,8388593,33292289,33550337,469762049,2130706433,3221225473, %U A336117 8588886017,137438691329,206158430209,2199023254529,6597069766657,562948879679489,7881299347898369,9007182074871809 %N A336117 Primes of the form q*2^h + 1, where q is a Mersenne prime. %F A336117 For all n >= 1, A335885(a(n)) <= 2. %o A336117 (PARI) %o A336117 A000265(n) = (n>>valuation(n,2)); %o A336117 isA000668(n) = (isprime(n)&&!bitand(n,1+n)); %o A336117 isA336117(n) = (isprime(n)&&isA000668(A000265(n-1))); %Y A336117 Cf. A000265, A000668, A334092, A335874, A335885, A336116. %K A336117 nonn %O A336117 1,1 %A A336117 _Antti Karttunen_, Jul 09 2020 %E A336117 More terms from _Jinyuan Wang_, Jul 11 2020