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 A240941 #41 Aug 16 2021 03:12:38
%S A240941 1,3,15,75,6308237,871506915,2465425275,2937864075,2948967789,
%T A240941 83313712623,195392257275,11126651718075,45237726869109,
%U A240941 2920008144904215
%N A240941 Numbers k that divide 2^k + 7.
%C A240941 Some larger terms: 213736983815110866141, 23423890178454972202084722709155. - _Max Alekseyev_, Sep 23 2016
%H A240941 OEIS Wiki, <a href="/wiki/2^n mod n">2^n mod n</a>
%e A240941 2^3 + 7 = 15 is divisible by 3. Thus 3 is a term of this sequence.
%t A240941 k = 1; lst = {1,3}; While[k < 2500000001, If[ PowerMod[2, k, k] + 7 == k, AppendTo[ lst, k]; Print[ k]]; k += 2]; lst (* _Robert G. Wilson v_, Aug 05 2014 *)
%o A240941 (PARI)
%o A240941 for(n=1,10^9,if(Mod(2,n)^n==Mod(-7,n),print1(n,", ")))
%Y A240941 Cf. A033981, A168415.
%K A240941 nonn,more,hard
%O A240941 1,2
%A A240941 _Derek Orr_, Aug 04 2014
%E A240941 a(7)-a(9) from _Robert G. Wilson v_, Aug 05 2014
%E A240941 a(10)-a(14) from _Max Alekseyev_, Sep 23 2016