A066331 Number of fixed hexagonal polyominoes with n cells and tree-like structure.

1, 3, 9, 29, 99, 348, 1260, 4644, 17382, 65822, 251655, 969819, 3762517, 14680890, 57567228, 226712655, 896252850, 3555116583, 14144563158, 56429348553, 225676776318, 904559526029, 3633045705543, 14618866104849, 58925096656511

Offset

1,2

Links

Table of n, a(n) for n=1..25.

G. Eising and B. J. Kooi, Cluster evolution and critical cluster sizes for the square and triangular lattice Ising models using lattice animals and Monte Carlo simulations, Phys. Rev. B 85 (2012), 214108. See the Supplemental Material, Table II, 0th row; beware the typo in a(8).

Sean A. Irvine, Java program (github)

Crossrefs

Cf. A001207 (all polyhexes), A038142 (free tree-like), A066158 (polyominoes).

Sequence in context: A001893 A238979 A151030 * A099780 A006134 A074526

Adjacent sequences: A066328 A066329 A066330 * A066332 A066333 A066334

Keyword

nonn,more

Author

Jan Kristian Haugland, Jan 01 2002

Extensions

a(16)-a(19) from Sean A. Irvine, Oct 08 2023

a(20)-a(25) from Eising and Kooi added by Andrei Zabolotskii, Apr 04 2026

Status

approved