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 A143887 #5 Oct 20 2014 18:35:10 %S A143887 1,2,3,35,60,2459,2907,447758,410457,237456332,154828648,342431110933, %T A143887 169227858597,1508376191950535,537887672115734 %N A143887 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric under horizontal reflection. %K A143887 nonn,more,hard %O A143887 0,2 %A A143887 _R. H. Hardin_, Sep 04 2008