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 A128403 #10 Jun 11 2021 04:58:39
%S A128403 1,2,4,6,8,11,12,20,22,24,40,42,44,60,66,78,84,88,120,132,156,168,212,
%T A128403 220,264,312,420,424,440,444,462,474,546,620,636,660,780,820,840,858,
%U A128403 888,924,948,1014,1060,1092,1218,1220,1240,1272,1320,1560,1640,1716
%N A128403 Numbers k such that k^2 divides 23^k-1.
%H A128403 Harvey P. Dale, <a href="/A128403/b128403.txt">Table of n, a(n) for n = 1..1000</a>
%t A128403 Join[{1},Select[Range[2000],PowerMod[23,#,#^2]==1&]] (* _Harvey P. Dale_, May 02 2015 *)
%Y A128403 Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128394, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128404.
%K A128403 nonn,less
%O A128403 1,2
%A A128403 _Alexander Adamchuk_, Mar 01 2007