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 A128396 #12 Mar 16 2022 12:38:28
%S A128396 1,3,5,15,21,39,55,105,155,165,195,205,273,465,609,615,903,915,1155,
%T A128396 1265,1365,1705,2067,2145,2255,2265,2373,2667,3045,3081,3255,3795,
%U A128396 4305,4515,4895,4965,5115,6045,6123,6355,6405,6765,7077,7455,7917,7995,10065
%N A128396 Numbers k such that k^2 divides 16^k-1.
%H A128396 Harvey P. Dale, <a href="/A128396/b128396.txt">Table of n, a(n) for n = 1..1000</a>
%t A128396 Select[Range[11000],Divisible[16^#-1,#^2]&] (* _Harvey P. Dale_, Dec 14 2010 *)
%t A128396 Join[{1},Select[Range[11000],PowerMod[16,#,#^2]==1&]] (* _Harvey P. Dale_, Mar 16 2022 *)
%Y A128396 Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128394, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128403, A128404.
%K A128396 nonn,less
%O A128396 1,2
%A A128396 _Alexander Adamchuk_, Mar 01 2007