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 A069539 #7 Jan 02 2012 16:43:15 %S A069539 4,40,112,220,400,1012,1120,1300,2020,2200,3100,4000,10012,10120,10300 %N A069539 Duplicate of A063997. %K A069539 dead %O A069539 0,1