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 A050991 #5 May 11 2007 03:00:00 %S A050991 9,15,21,33,39,51,57,63,69,87,93,111,123,129,141,159,177,183,195,201 %N A050991 Duplicate of A033553. %K A050991 dead %O A050991 1,1