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 A138874 #29 Aug 06 2018 05:36:09 %S A138874 6,28,96,28,36,56,28,28,76,16,28,28,76,28,28,28,76,56,36,28,16,76,36, %T A138874 56,76,16,56,28,28,16,28,28,36,28,16,76,56,36,56,28,28,28,56,56,28,76, %U A138874 16 %N A138874 Last two digits of the n-th even perfect number. %H A138874 Édouard Lucas: Théorie des nombres. Vol. 1: Le calcul des nombres entiers. Le calcul des nombres rationnels. La divisibilité arithmétique. Paris: Gauthier-Villars, 1891, Nr. 229 (Théorème de Fermat), Ex. V, <a href="http://www.archive.org/stream/thoriedesnombre00lucagoog#page/n435/mode/2up">p. 424-425</a>. %H A138874 Omar E. Pol, <a href="http://www.polprimos.com/#Los%20n%C3%BAmeros%20perfectos">Los numeros perfectos</a> %Y A138874 Cf. A000396, A080173, A104511, A138875. %K A138874 base,nonn %O A138874 1,1 %A A138874 _Omar E. Pol_, Apr 02 2008 %E A138874 Definition changed (inserting the word "even") and a(39)-a(47) added by _Ivan Panchenko_, Aug 04 2018