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 A128405 #15 Jun 06 2021 09:01:37
%S A128405 1,11,253,11891,768361,36112967,61488361,154261943,2936791979,
%T A128405 61057324141,67546215517,107342336783,186740152357,347036920549,
%U A128405 429306186947,468493520891,635974117823,797688507253,3174672129299
%N A128405 Numbers k such that k^2 divides 12^k - 1.
%C A128405 11 divides all except the first term.
%C A128405 All terms are congruent to +-1 (mod 12). - _Robert G. Wilson v_, Dec 19 2014
%t A128405 fQ[n_] := Mod[ PowerMod[12, n, n^2] - 1, n^2] == 0; k = 1; lst = {}; While[k < 100000001, If[ fQ@ k, AppendTo[lst, k]; Print@ k]; k += 10; If[ fQ@ k, AppendTo[lst, k]; Print@ k]; k += 2]; lst (* _Robert G. Wilson v_, Dec 19 2014 *)
%Y A128405 Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128393, A128394, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128403, A128404.
%K A128405 nonn,less
%O A128405 1,2
%A A128405 _Alexander Adamchuk_, Mar 01 2007
%E A128405 a(6)-a(8) from _Farideh Firoozbakht_, Mar 05 2007
%E A128405 Terms a(9) onward from _Max Alekseyev_, May 06 2010