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 A128395 #18 May 21 2024 01:14:17
%S A128395 1,2,4,7,8,14,16,28,56,112,136,272,452,812,904,952,1624,1808,1904,
%T A128395 3164,3248,6328,11912,12656,15368,18632,23824,27608,30736,37264,47908,
%U A128395 55216,60248,83384,91756,95816,102604,107576,113936,120496,130424,166768
%N A128395 Numbers k such that k^2 divides 15^k-1.
%H A128395 Amiram Eldar, <a href="/A128395/b128395.txt">Table of n, a(n) for n = 1..640</a>
%t A128395 a={1};For[n=1,n<200000,n++,If[PowerMod[15,n,n^2]==1, AppendTo[a, n]]]; a (* _Stefan Steinerberger_, Jun 10 2007 *)
%t A128395 Join[{1},Select[Range[167000],PowerMod[15,#,#^2]==1&]] (* _Harvey P. Dale_, Sep 14 2020 *)
%o A128395 (PARI) is(k) = Mod(15, k^2)^k == 1; \\ _Amiram Eldar_, May 21 2024
%Y A128395 Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128403, A128404.
%K A128395 nonn,less
%O A128395 1,2
%A A128395 _Alexander Adamchuk_, Mar 01 2007
%E A128395 More terms from _Stefan Steinerberger_, Jun 10 2007