A121220 Number of fixed hexagonal polygons (or benzenoids) with n cells.

1, 3, 11, 44, 186, 813, 3640, 16590, 76663, 358195, 1688784, 8022273, 38351973, 184353219, 890371070, 4318095442, 21018564402, 102642526470, 502709028125, 2468566918644, 12150769362815, 59937663454017

Offset

1,2

Links

Vaclav Kotesovec, Table of n, a(n) for n = 1..50 (terms 1..46 from N. J. A. Sloane) [all terms from Jensen link]

I. Jensen, First 46 terms

Iwan Jensen, A parallel algorithm for the enumeration of benzenoid hydrocarbons, arXiv:0808.0963v1 [cond-mat.stat-mech], 2007-2008.

Markus Vöge, Anthony J. Guttmann, and Iwan Jensen, On the Number of Benzenoid Hydrocarbons, Journal of Chemical Information and Computer Sciences, 42(3) (2002), 456-466. See Table 2 under the B_h column on page 462.

Formula

See equation 11 on page 463 of the paper by Markus Voege, Anthony J. Guttmann and Iwan Jensen for an asymptotic form for a(n).

Crossrefs

Cf. A018190.

Sequence in context: A361764 A167012 A167013 * A068091 A001207 A319156

Adjacent sequences: A121217 A121218 A121219 * A121221 A121222 A121223

Keyword

nonn

Author

Parthasarathy Nambi, Aug 20 2006

Extensions

More terms from N. J. A. Sloane, Aug 25 2006

Status

approved