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 A332549 #18 Feb 22 2020 21:53:18
%S A332549 5,6,8,11,12,23,47,96,191,192,383,768,6143,12288,786431,786432,
%T A332549 3221225472,51539607551,206158430208,824633720831,6597069766656,
%U A332549 26388279066623,108086391056891903,55340232221128654847,221360928884514619392,226673591177742970257407
%N A332549 Numbers k such that A332547(k) = 3.
%C A332549 The numbers k such that A332547(k) = 1 are given by A068194, a sequence of interest to Mersenne and Fermat, so this sequence may also be interesting.
%C A332549 The factors of the initial terms are 5, 2*3, 2^3, 11, 2^2*3, 23, 47, 2^5*3, 191, 2^6*3, 383, 2^8*3, 6143, 2^12*3, 786431, 2^18*3, ...
%C A332549 There are essentially two cases. Firstly n can be an odd prime and n+1 of the form 3*2^k. These are the terms of A007505 with 2 excluded. Otherwise n can be of the form 3*2^k and n+1 a prime. These are 1 less than the terms of A039687. In addition, 8 is a term which is a special case. - _Andrew Howroyd_, Feb 21 2020
%o A332549 (PARI) upto(n)={Set(concat([if(n<8,[],[8]), select(isprime, [3*2^k-1 |k<-[1..logint((n+1)\3, 2)]]), select(p->isprime(p+1), [3*2^k |k<-[1..logint(n\3, 2)]])]))} \\ _Andrew Howroyd_, Feb 21 2020
%Y A332549 Cf. A007505, A039687, A068194, A332547.
%K A332549 nonn
%O A332549 1,1
%A A332549 _N. J. A. Sloane_, Feb 21 2020
%E A332549 Terms a(17) and beyond from _Andrew Howroyd_, Feb 21 2020