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 A143874 #5 Oct 20 2014 18:31:02 %S A143874 1,2,3,7,18,111,497,4630,38327,702227,10398834 %N A143874 Number of ways of placing kings with no more than 1 mutual attack on an n X n chessboard symmetric under 180 degree rotation. %K A143874 nonn,more,hard %O A143874 0,2 %A A143874 _R. H. Hardin_, Sep 04 2008