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

Author

Parthasarathy Nambi, Aug 20 2006

Keywords

• nonn

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.

Crossrefs

Cf. A018190.

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).

Extensions

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