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 A143883 #5 Oct 20 2014 18:34:00 %S A143883 1,2,7,29,160,1135,10529,125770,1963039,39868375,1061669314, %T A143883 37110747097,1708827058427 %N A143883 Number of ways of placing kings with no more than 3 mutual attacks on an n X n chessboard symmetric about main diagonal. %K A143883 nonn,more,hard %O A143883 0,2 %A A143883 _R. H. Hardin_, Sep 04 2008