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 A006726 M4523 #15 Jul 07 2015 17:42:48 %S A006726 1,8,40,168,676,2672,10376,39824,151878,576656,2181496,8229160, %T A006726 30974700,116385088,436678520,1636472360,6126647748 %N A006726 Number of n-celled polygons with perimeter 2n on square lattice. %D A006726 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A006726 I. G. Enting and A. J. Guttmann, <a href="http://dx.doi.org/10.1007/BF01112757">On the area of square lattice polygons</a>, J. Statist. Phys., 58 (1990), 475-484. %K A006726 nonn %O A006726 4,2 %A A006726 _N. J. A. Sloane_, _Simon Plouffe_