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A006861
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Number of directed site animals on hexagonal lattice.
(Formerly M0786)
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0
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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; internal format)
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OFFSET
| 1,2
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COMMENTS
| The hexagonal lattice is the familiar 2-dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
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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).
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LINKS
| G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2
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CROSSREFS
| Sequence in context: A079116 A109222 A191789 * A052956 A008930 A164362
Adjacent sequences: A006858 A006859 A006860 * A006862 A006863 A006864
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KEYWORD
| nonn
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AUTHOR
| Simon Plouffe, N. J. A. Sloane (njas(AT)research.att.com).
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