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 A048857 #3 Jun 12 2004 03:00:00 %S A048857 0,3,7,5,31,7,127,17,73,31,89,13,8191,127,151,257,131071,73,524287,41 %N A048857 A005420 prefixed with a 0. %K A048857 dead %O A048857 1,2