A006861 Number of directed site animals on hexagonal lattice. (Formerly M0786)

1, 2, 3, 6, 11, 21, 40, 77, 149, 289, 563, 1099, 2152, 4222, 8299, 16339, 32217, 63612, 125753, 248870, 493015, 977576, 1940042, 3853117, 7658211, 15231219, 30312012, 60360046, 120260317

Offset

1,2

Comments

The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.

References

D. Dhar et al., Enumeration of directed site animals on two-dimensional lattices, J. Phys. A 15 (1982), L279-L284.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..29.

G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2

Crossrefs

Sequence in context: A191789 A371790 A306575 * A052956 A351972 A298118

Adjacent sequences: A006858 A006859 A006860 * A006862 A006863 A006864

Keyword

nonn

Author

Simon Plouffe and N. J. A. Sloane

Status

approved