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%I #2 Mar 30 2012 17:25:49
%S 0,1,1,2,2,3,3,6,7,11,14,21,23,41,50,80,94,156,189,310,365,615,748,
%T 1237,1459,2488,3023,5059,5994,10296,12511,21149,25100,43451,52870
%N Number of free hexagonal polygons of symmetry class D_(2h) and area n.
%D 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 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 nonn
%O 1,4
%A _Parthasarathy Nambi_, Aug 19 2006