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 A086821 #4 May 11 2007 03:00:00 %S A086821 1,1,1,3,7,15,35,87,217,547,1417,3735,9911,26513,71581,194681,532481 %N A086821 Duplicate of A007576. %K A086821 dead %O A086821 0,4