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A006861 Number of directed site animals on hexagonal lattice.
(Formerly M0786)
0
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 (list; graph; refs; listen; history; text; internal format)
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: A109222 A191789 A306575 * A052956 A298118 A008930

Adjacent sequences:  A006858 A006859 A006860 * A006862 A006863 A006864

KEYWORD

nonn

AUTHOR

Simon Plouffe and N. J. A. Sloane.

STATUS

approved

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Last modified December 2 16:46 EST 2020. Contains 338877 sequences. (Running on oeis4.)