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 A197553 #9 Dec 05 2014 03:00:32 %S A197553 1,2,7,24,99,416,1852,8386,38797,181530,858560,4092031,19636098, %T A197553 94750833 %N A197553 Number of free poly-IH12-tiles (holes allowed) with n cells. %C A197553 Equivalently, polyhexes where two polyhexes are considered equivalent if and only if they are related by a translation or a reflection or glide reflection in a line in one fixed direction perpendicular to the sides of the hexagons. %D A197553 Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Sections 6.2 and 9.4. %Y A197553 Cf. A000228, A001207, A006535, A057973, A197549, A197550, A197551, A197552, A197554. %K A197553 hard,nonn %O A197553 1,2 %A A197553 _Joseph Myers_, Oct 16 2011