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 A128404 #19 Jun 11 2021 04:58:15
%S A128404 1,23,1081,2870377,7009273,15954479,134907719,329435831,537539141,
%T A128404 15001987199,874750261127,1991103024721,4272172921319,4862143429729,
%U A128404 7933540182019,12816504745411,41113262272969,67084347257659
%N A128404 Numbers k such that k^2 divides 24^k-1.
%C A128404 23 divides all terms except the first.
%t A128404 a={}; Do[r=(24^n-1)/n^2; If[r==IntegerPart[r], AppendTo[a, n]], {n, 1, 10^3}]; a (* _Vladimir Joseph Stephan Orlovsky_, Aug 07 2008 *)
%Y A128404 Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128394, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128403.
%K A128404 nonn,less
%O A128404 1,2
%A A128404 _Alexander Adamchuk_, Mar 01 2007
%E A128404 a(5)-a(6) from _Farideh Firoozbakht_, Mar 05 2007
%E A128404 a(7)-a(10) from _Ryan Propper_, Feb 23 2008
%E A128404 Terms a(11) onward from _Max Alekseyev_, May 06 2010