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 A056882 #14 Oct 10 2022 04:33:27 %S A056882 0,0,0,0,0,0,1,1,0,1,2,1,2,3,4,4,6,7,12,12,17,18,33,34,51,52,93,100, %T A056882 154,152,276,300,474,460,846,929,1491,1431,2667,2956 %N A056882 Number of n-celled polyominoes without holes, symmetric about diagonal 2. %H A056882 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/animals.html">Enumeration of polyominoes</a> %Y A056882 Cf. A000104, A056878 (with holes allowed). %K A056882 nonn,more %O A056882 1,11 %A A056882 _N. J. A. Sloane_, Sep 03 2000 %E A056882 a(29)-a(40) from _John Mason_, Oct 10 2022