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 A031989 #14 Oct 18 2018 21:36:49 %S A031989 0,1,2,3,5,6,7,10,11,15,21,22,23,26,27,31,42,43,47,63,85,86,87,90,91, %T A031989 95,106,107,111,127,170,171,175,191,255,341,342,343,346,347,351,362, %U A031989 363,367,383,426,427,431,447,511,682,683,687,703 %N A031989 Duplicate of A023746. %K A031989 dead %O A031989 1,3