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 A240942 #28 Aug 17 2021 02:17:20 %S A240942 1,11,121,323,117283,432091,4132384531,15516834659,15941429747, %T A240942 98953554491,3272831195051,7362974489179,26306805687881, %U A240942 33869035218491,280980898827691 %N A240942 Numbers k that divide 2^k + 9. %C A240942 No other terms below 10^15. Some larger terms: 53496121130110340001650284048539458491, 136243118444105327963550175410279542214992801356720577. - _Max Alekseyev_, Sep 29 2016 %H A240942 OEIS Wiki, <a href="/wiki/2^n mod n">2^n mod n</a> %e A240942 2^11 + 9 = 2057 is divisible by 11. Thus 11 is a term of this sequence. %p A240942 select(n -> 9 + 2 &^ n mod n = 0, [$1..10^6]); # _Robert Israel_, Aug 04 2014 %o A240942 (PARI) for(n=1,10^9, if(Mod(2,n)^n==-9, print1(n,", "); ); ); %Y A240942 Cf. A051447, A188165, A245594, A245319, A245318, A244673. %K A240942 nonn,more,hard %O A240942 1,2 %A A240942 _Derek Orr_, Aug 04 2014 %E A240942 a(7)-a(10) from _Lars Blomberg_, Nov 05 2014 %E A240942 a(11)-a(15) from _Max Alekseyev_, Sep 29 2016