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 A075216 #11 Dec 05 2014 02:41:58 %S A075216 1,2,8,24,62,291,539,2625,6177,21923,37721,238267,299203,1338140, %T A075216 3492733 %N A075216 Number of polyiamonds with 2n cells that tile the plane by translation. %C A075216 Polyiamonds with an odd number of cells have different numbers of triangles with the two orientations and so cannot tile by translation. %D A075216 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4. %H A075216 Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyiamond tiling</a> %Y A075216 Cf. A071332, A075217, A075218, A075219, A075220, A075221, A075222, A075223, A075224, A075198, A075207. %K A075216 hard,nonn %O A075216 1,2 %A A075216 _Joseph Myers_, Sep 08 2002 %E A075216 More terms from _Joseph Myers_, Nov 11 2003 %E A075216 a(15) (30-iamonds) from _Joseph Myers_, Nov 21 2010