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 A089456 #4 Apr 07 2015 10:48:39
%S A089456 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,8,179,2509,25609,214932,1578984,
%T A089456 10536260,65411645,383981499,2156114468
%N A089456 Number of n-celled polyominoes with exactly 4 holes.
%H A089456 Tomás Oliveira e Silva, <a href="http://www.ieeta.pt/%7Etos/animals/a44.html">Animal enumerations on the {4,4} Euclidean tiling</a>
%Y A089456 Cf. A001419, A057418, A089454, A089455, A089457, A089458.
%K A089456 hard,nonn
%O A089456 1,17
%A A089456 _Joseph Myers_, Nov 04 2003