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 A051921 #5 May 11 2007 03:00:00 %S A051921 1,1,3,16,131,1496,22482,426833,9934563,277006192,9085194458 %N A051921 Duplicate of A023998. %K A051921 dead %O A051921 0,3