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 A075217 #11 Dec 05 2014 02:42:35 %S A075217 0,0,0,0,1,22,38,504,1468,6945,11046,115186,119496,677774,2013619 %N A075217 Number of polyiamonds with 2n cells that tile the plane by translation but not by 180-degree rotation (Conway criterion). %C A075217 Polyiamonds with an odd number of cells have different numbers of triangles with the two orientations and so cannot tile by translation. %D A075217 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4. %H A075217 Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyiamond tiling</a> %Y A075217 Cf. A071332, A075216, A075218, A075219, A075220, A075221, A075222, A075223, A075224, A075199, A075208. %K A075217 hard,nonn %O A075217 1,6 %A A075217 _Joseph Myers_, Sep 08 2002 %E A075217 More terms from _Joseph Myers_, Nov 11 2003 %E A075217 a(15) (30-iamonds) from _Joseph Myers_, Nov 21 2010