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 A219341 #12 Feb 16 2025 08:33:18
%S A219341 2,3,0,11,397,839,1459,2081,7297,53849,3499,70589,792277,20399,
%T A219341 11173873,929057,232591,6782759,5834299,26812151,40269673,88529891,
%U A219341 368454343,616767917,1167319801,709939943,38151887029,38617336361,23280518791,168046587719,882701485339
%N A219341 Least prime k such that k*2^n + 1 divides 2^k - 1, or 0 if no such prime exists.
%C A219341 If a(n) > 0, then a(n)*2^n + 1 is in A122094.
%H A219341 G. L. Honaker, Jr. and Chris Caldwell, <a href="https://t5k.org/curios/cpage/18226.html">Prime Curios! 232591</a>
%H A219341 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/MersenneNumber.html">Mersenne Number</a>
%t A219341 lst = {}; Do[k = 2; If[n == 2, AppendTo[lst, 0], While[True, If[PrimeQ[k], f = k*2^n + 1; If[PrimeQ[f] && PowerMod[2, k, f] == 1, AppendTo[lst, k]; Break[]]]; k++]], {n, 0, 13}]; lst
%Y A219341 Cf. A001348, A002144.
%K A219341 nonn
%O A219341 0,1
%A A219341 _Arkadiusz Wesolowski_, Nov 18 2012
%E A219341 a(26)-a(30) from _Jason Yuen_, May 24 2024