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 A143879 #5 Oct 20 2014 18:32:42 %S A143879 1,2,3,7,12,41,85,434,1009,7325,21498,219307,803859,11370922 %N A143879 Number of ways of placing kings with no more than 2 mutual attacks on an n X n chessboard symmetric about both diagonal and antidiagonal. %K A143879 nonn,more,hard %O A143879 0,2 %A A143879 _R. H. Hardin_, Sep 04 2008