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 A133015 #3 Mar 11 2014 01:34:10 %S A133015 1,36,101521,28364555,667891105120,136153171190210231, %T A133015 253276300325351378406,435465496528561595630666, %U A133015 7037417808208619039469901035,1081112811761225127513261378143114851540 %N A133015 Concatenation of next n positive triangular numbers. %H A133015 Omar E. Pol, <a href="http://www.polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>. %Y A133015 Cf. A053067, A053068. Triangular numbers: A000217. %K A133015 easy,nonn,base %O A133015 1,2 %A A133015 _Omar E. Pol_, Oct 19 2007