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 A069696 #5 Dec 05 2013 19:55:17 %S A069696 0,1,3,6,10,15,21,28,36,45,55,66,78,91,741,946,6441,544446 %N A069696 Triangular numbers with internal digits 4. %C A069696 For proof of finiteness see A069693. %Y A069696 Cf. A069675 to A069684, A069693 to A069700. %K A069696 fini,full,nonn,base %O A069696 1,3 %A A069696 _Amarnath Murthy_, Apr 06 2002 %E A069696 Extended by _Robert G. Wilson v_, Apr 07 2002