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 A143888 #5 Oct 20 2014 18:35:32 %S A143888 1,2,1,11,4,101,29,1592,263,43578,4424,1972239,117557,159790891, %T A143888 5394252,22035879309,430235439 %N A143888 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric under horizontal and vertical reflection. %K A143888 nonn,more,hard %O A143888 0,2 %A A143888 _R. H. Hardin_, Sep 04 2008