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 A089416 #5 Aug 20 2017 23:16:27 %S A089416 1,2,4,5,11,17,21,30,52,74 %N A089416 Odd-indexed terms of A089413. %K A089416 nonn %O A089416 0,2 %A A089416 _Antti Karttunen_, Nov 29 2003