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 A143872 #5 Oct 20 2014 18:30:23 %S A143872 1,2,5,15,62,329,2307,21482,264021,4334045,94435970,2750500857, %T A143872 106769182533 %N A143872 Number of ways of placing kings with no more than 1 mutual attack on an n X n chessboard symmetric about main diagonal. %K A143872 nonn,more,hard %O A143872 0,2 %A A143872 _R. H. Hardin_, Sep 04 2008