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 A057973 #11 Oct 19 2017 03:13:52 %S A057973 1,2,5,16,55,225,949,4269,19500,91115,429742,2047660,9820197,47383255, %T A057973 229725560,1118568692,5466616025,26804560282,131817042605,649952289243 %N A057973 Number of polybricks: number of ways to arrange n 1 X 2 "bricks" in a wall (see illustrations). %C A057973 The tiling of bricks is topologically the same as that by regular hexagons and this sequence can also be seen as counting polyhexes where two polyhexes are equivalent iff they are related by a symmetry that is also a symmetry of the tiling by bricks. %D A057973 Other references on polyforms are: www.mathpuzzle.com, Solomon W. Golomb, Ed Pegg, Eric Weisstein, David A. Klarner (Packing rectangles) and Michael Reid [These references should be expanded! - _N. J. A. Sloane_] %H A057973 Brendan Owen and Livio Zucca, <a href="http://www.iread.it/lz/polymultiforms2.html">Polyform generation</a> %H A057973 Brendan Owen and Livio Zucca, <a href="/A057973/a057973a.gif">The 16 polybricks of order 4</a> %H A057973 N. J. A. Sloane, <a href="/A057973/a057973.gif">The polybricks of orders 1, 2 and 3</a> %K A057973 nonn,nice %O A057973 1,2 %A A057973 Warren Power (wjpnply(AT)hotmail.com), Oct 21 2000 %E A057973 More terms from _Don Reble_, Nov 01 2001 %E A057973 Corrected and extended by _Joseph Myers_, Sep 21 2002