OFFSET
1,4
REFERENCES
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.
EXAMPLE
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.
CROSSREFS
KEYWORD
nonn
AUTHOR
Parthasarathy Nambi, Aug 19 2006
STATUS
approved