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 A116632 #20 Apr 10 2020 22:49:20
%S A116632 1,2,3,6,15,75,219,1335,3246,4975,5475,7775,8922,28614,67675,69998,
%T A116632 103135,313609,548983,624193,6539595,13193562,26383395,111892866,
%U A116632 315953675,5330142066,33738816835,66899423586,336966134829,645835313441,742199683475,1244107219389,10187548490537,760354210440662
%N A116632 Positive integers n such that 13^n == 7 (mod n).
%C A116632 No other terms below 10^15. - _Max Alekseyev_, Oct 30 2018
%C A116632 Some larger terms: 6584692157923407917184426, 3226231185229904054184099310127719809, 30643479515551752620928357020812679775, 5890087594520845596744547263586007316572563275. - _Max Alekseyev_, Oct 30 2018
%t A116632 Join[{1, 2, 3, 6}, Select[Range[1, 9000], Mod[13^#, #] == 7 &]] (* _G. C. Greubel_, Nov 19 2017 *)
%t A116632 Join[{1, 2, 3, 6}, Select[Range[10000000], PowerMod[13, #, #] == 7 &]] (* _Robert Price_, Apr 10 2020 *)
%o A116632 (PARI) isok(n) = Mod(13, n)^n == 7; \\ _Michel Marcus_, Nov 19 2017
%Y A116632 Cf. A116609, A116611, A116620, A116621, A116622, A116629, A116630, A116631.
%K A116632 nonn
%O A116632 1,2
%A A116632 _Zak Seidov_, Feb 19 2006
%E A116632 More terms from _Ryan Propper_, Mar 30 2007
%E A116632 Terms 1,2,3,6 prepended and a(27)-a(34) added by _Max Alekseyev_, Jun 30 2011, Oct 30 2018