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 A139470 #4 Aug 18 2017 16:11:18 %S A139470 5,5,20,60,180,570 %N A139470 Incorrect version of A154640 and A154644. %K A139470 dead %O A139470 1,1