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 A056884 #14 Oct 11 2022 08:35:02 %S A056884 0,0,0,1,5,20,84,311,1165,4276,15802,58280,216070,803116,2997360, %T A056884 11221443,42147842,158749808,599513836,2269390757,8609258335, %U A056884 32725209938,124621150623,475367241264,1816100804241,6948222137523,26618662003342,102102765921611,392095326233619,1507357249572269,5800716924062537,22344021033377558 %N A056884 Number of asymmetric n-celled polyominoes without holes. %H A056884 John Mason, <a href="/A056884/b056884.txt">Table of n, a(n) for n = 1..40</a> %H A056884 Tomás Oliveira e Silva, <a href="http://sweet.ua.pt/tos/animals.html">Enumeration of polyominoes</a> %F A056884 a(n) = A000104(n) - (A056879(n) + A056881(n) + A056883(n) + A056880(n) + A056882(n) + A357647(n) + A357648(n)) %Y A056884 Cf. A000104, A006749 (with holes allowed). %K A056884 nonn %O A056884 1,5 %A A056884 _N. J. A. Sloane_, Sep 03 2000 %E A056884 a(27)-a(32) from _John Mason_, Oct 11 2022