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 A075200 #12 Dec 05 2014 03:01:49 %S A075200 1,1,2,5,9,24,41,121,212,520,773,2577,3037,8081,13954,32124,41695, %T A075200 118784,150188,411484,604304,1305265,1954823,5326890,7331606 %N A075200 Number of polyominoes with n cells that tile the plane both by translation and by 180-degree rotation (Conway criterion). %D A075200 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4. %H A075200 Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyomino tiling</a> %Y A075200 Cf. A054359, A075198, A075199, A075201, A075202, A075203, A075204, A075205, A075206, A075209, A075218. %K A075200 hard,nonn %O A075200 1,3 %A A075200 _Joseph Myers_, Sep 08 2002 %E A075200 More terms from _Joseph Myers_, Nov 04 2003 %E A075200 a(24) and a(25) from _Joseph Myers_, Nov 17 2010