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 A075219 #11 Dec 05 2014 02:43:13 %S A075219 1,0,1,1,4,4,21,32,111,200,462,1162,1875,4195,9410,17978,24034,73175, %T A075219 79925,251808,358096,631919,796571,3104082,2980476,6088310,10167660, %U A075219 23661369,21477012,84485584 %N A075219 Number of polyiamonds with n cells that tile the plane by 180-degree rotation (Conway criterion) but not by translation. %D A075219 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4. %H A075219 Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyiamond tiling</a> %Y A075219 Cf. A071332, A075216, A075217, A075218, A075220, A075221, A075222, A075223, A075224, A075201, A075210. %K A075219 hard,nonn %O A075219 1,5 %A A075219 _Joseph Myers_, Sep 08 2002 %E A075219 More terms from _Joseph Myers_, Nov 11 2003 %E A075219 a(29) and a(30) from _Joseph Myers_, Nov 21 2010