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 A019473 #68 Aug 21 2020 09:15:50
%S A019473 0,0,0,2,1,5,4,9,10,25,46,121,240,619,1353,3286,7773,19044,45759,
%T A019473 112243,273188,672172,1646147,4051732,9971377,24619307,60823008,
%U A019473 150613157,373188952,926068847,2299616637,5716948683,14223867298,35422864104
%N A019473 Number of stable n-celled patterns ("still lifes") in Conway's Game of Life, up to rotation and reflection.
%C A019473 This sequence only counts still lifes that cannot be broken down into 2 or more smaller still lifes. That is, it only counts "strict" still lifes (contrast with A056613). - _Nathaniel Johnston_, Dec 11 2019
%H A019473 S. Ekström, <a href="http://conwaylife.com/forums/viewtopic.php?p=38931#p38931">Enumerating Still Lifes (in C)</a>
%H A019473 N. D. Elkies, <a href="https://arxiv.org/abs/math/9905194">The still-Life density problem and its generalizations</a>, arXiv:math/9905194 [math.CO], 1999.
%H A019473 H. Koenig, <a href="http://www.pentadecathlon.com/objects/class1/class1.php">Stable Objects</a> (another version of this sequence)
%H A019473 R. Munafo, <a href="http://www.mrob.com/pub/math/seq-a019473.html">Still-Lifes with N cells in Conway's game of Life</a>
%H A019473 Mark D. Niemiec, <a href="http://codercontest.com/mniemiec/objcount.htm">Life Object Counts</a>
%H A019473 R. C. Schroeppel, <a href="http://www.experimentalmath.info/workshop2004/schroeppel-talk.pdf">A few mathematical experiments</a>
%H A019473 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GameofLife.html">Game of Life</a>
%e A019473 a(4)=2 because the block and the tub are the only 4-cell still lifes.
%Y A019473 Cf. A056613, A056614, A056605, A330283.
%K A019473 hard,nonn,nice
%O A019473 1,4
%A A019473 _Robert Munafo_
%E A019473 More terms from _Stephen A. Silver_, Dec 11 1999
%E A019473 a(24) corrected, at the suggestion of Mark Niemiec, by _Nathaniel Johnston_, Aug 26 2016
%E A019473 a(24)-a(28) corrected, using data computed by Simon Ekström, by _Adam P. Goucher_, Jan 08 2017
%E A019473 a(31)-a(32) from _Nathaniel Johnston_, using a script made by Simon Ekström, May 25 2017
%E A019473 a(33) from _Nathaniel Johnston_, using a script made by Simon Ekström, Apr 05 2019
%E A019473 a(34) from _Nathaniel Johnston_, using a script made by Simon Ekström, Jan 09 2020