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 A075206 #13 Dec 05 2014 03:03:56 %S A075206 0,0,0,0,0,0,0,1,9,44,108,222,431,900,1157,2258,1381,7429,5542,18306, %T A075206 22067,47849,10542,202169,28977 %N A075206 Number of anisohedral polyominoes with n cells. %C A075206 A tiling is isohedral if the symmetries of the tiling act transitively on the tiles; a shape is anisohedral if it tiles the plane, but not isohedrally. %D A075206 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4. %H A075206 Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyomino tiling</a> %Y A075206 Cf. A054359, A075198, A075199, A075200, A075201, A075202, A075203, A075204, A075205, A075215, A075224. %K A075206 hard,nonn %O A075206 1,9 %A A075206 _Joseph Myers_, Sep 08 2002 %E A075206 More terms from _Joseph Myers_, Nov 04 2003 %E A075206 a(24) and a(25) from _Joseph Myers_, Nov 17 2010