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 A121211 #2 Mar 30 2012 17:25:49 %S A121211 0,1,1,2,2,3,3,6,7,11,14,21,23,41,50,80,94,156,189,310,365,615,748, %T A121211 1237,1459,2488,3023,5059,5994,10296,12511,21149,25100,43451,52870 %N A121211 Number of free hexagonal polygons of symmetry class D_(2h) and area n. %D A121211 Markus Voege, Anthony J. Guttmann and Iwan Jensen, "On the number of benzenoid hydrocarbons", J. Chem. Inf. Comput. Sci., (2002), vol. 42, 456-466. See Table 3 under the D_(2h) column. %e A121211 If n=10 then the number of free hexagonal polygons of symmetry class D_(2h) is 11 which is the tenth term in the sequence. %K A121211 nonn %O A121211 1,4 %A A121211 _Parthasarathy Nambi_, Aug 19 2006