

A120991


Number of free hexagonal polygons of symmetry class C_(2c) and area n.


2



0, 0, 1, 1, 9, 12, 39, 61, 178, 274, 796, 1251, 3578, 5692, 16290, 26069, 74980, 120676, 348564, 563503, 1635175, 2652445, 7729807, 12574028, 36784467, 59975232, 176063801, 287613473, 846967739, 1385815492, 4092516853, 6705360813, 19852731854, 32565589836, 96642900684
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OFFSET

1,5


REFERENCES

Markus Voege, Anthony J. Guttmann and Iwan Jensen, "On the number of benzenoid hydrocarbons", J. Chem. Inf. Comput. Sci., (2002), vol. 42, 456466. See Table 3 under the C_(2c) column.


LINKS

Table of n, a(n) for n=1..35.


EXAMPLE

If n=10 then the number of free hexagonal polygons of symmetry class C_(2c) is 274 which is the tenth term in the sequence.


CROSSREFS

Sequence in context: A216297 A024312 A024877 * A253088 A072308 A045769
Adjacent sequences: A120988 A120989 A120990 * A120992 A120993 A120994


KEYWORD

nonn


AUTHOR

Parthasarathy Nambi, Aug 19 2006


EXTENSIONS

More terms from N. J. A. Sloane, Aug 27 2006


STATUS

approved



