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 A075212 #11 Dec 05 2014 02:41:16 %S A075212 1,1,3,7,21,75,257,930,3104,9265,21304,81392,139612,427454,1176912, %T A075212 2491134,4319362,16243200,21965930,76738851,158374741 %N A075212 Number of polyhexes with n cells that tile the plane by translation or by 180-degree rotation (Conway criterion). %D A075212 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4. %H A075212 Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyhex tiling</a> %Y A075212 Cf. A070766, A075207, A075208, A075209, A075210, A075211, A075213, A075214, A075215, A075203, A075221. %K A075212 hard,nonn %O A075212 1,3 %A A075212 _Joseph Myers_, Sep 08 2002 %E A075212 More terms from _Joseph Myers_, Nov 08 2003 %E A075212 a(20) and a(21) from _Joseph Myers_, Nov 21 2010