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 A098980 #4 Jun 29 2008 03:00:00 %S A098980 1,3,9,21,363,2161,4839,49521,105994 %N A098980 Duplicate of A007647. %K A098980 dead %O A098980 1,2