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 A128684 #11 Jun 08 2021 02:22:27 %S A128684 1,3,111,24753,1770231,23401797,39402669,65498547,298100379,440377293, %T A128684 1788478509,5218600731,8786795187,14606175981,24342867543,45340639419, %U A128684 98204136339,5032808252679,5293823142513,6241891310439,7013907181779 %N A128684 Numbers k such that k^3 divides 11^(k^2) + 1. %C A128684 3 divides a(n) for n > 1. %t A128684 Select[Range[5*10^6], Mod[ 11^(#^2)+1, #^3]==0 &] (* _G. C. Greubel_, Jan 18 2018 *) %Y A128684 Cf. A127263, A128677, A128678, A128679, A128680, A128681, A128682, A128683, A128685. %K A128684 nonn %O A128684 1,2 %A A128684 _Alexander Adamchuk_, Mar 31 2007 %E A128684 a(5) from J. Mulder (jasper.mulder(AT)planet.nl), Jan 26 2010 %E A128684 Terms from a(6) onward from _Max Alekseyev_, May 14 2010