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 A128402 #18 Jun 11 2021 04:58:55
%S A128402 1,3,7,21,39,273,507,3081,3549,21567,40053,78117,280371,343239,546819,
%T A128402 1015521,2056899,2402673,5998317,6171243,7108647,8740173,12338859,
%U A128402 14398293,18988203,27115881,41988219,43198701,47727771,55431363
%N A128402 Numbers k such that k^2 divides 22^k-1.
%p A128402 select(t -> 22 &^ t - 1 mod t^2 = 0, [seq(2*k+1,k=0..10^6)]); # _Robert Israel_, Jan 23 2015
%t A128402 a={}; Do[r=(22^n-1)/n^2; If[r==IntegerPart[r], AppendTo[a, n]], {n, 1, 10^3}]; a (* _Vladimir Joseph Stephan Orlovsky_, Aug 07 2008 *)
%o A128402 (PARI) { forstep(m=11,10^8,2, if( Mod(22,m^2)^m==1, print(m) ) ) } \\ _Max Alekseyev_, Oct 18 2008
%Y A128402 Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128394, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128403, A128404.
%K A128402 nonn,less
%O A128402 1,2
%A A128402 _Alexander Adamchuk_, Mar 01 2007
%E A128402 a(14)-a(30) from _Max Alekseyev_, Oct 18 2008