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Search: id:A006861
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| A006861 |
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Number of directed site animals on hexagonal lattice.
(Formerly M0786)
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+0
1
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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; listen)
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OFFSET
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1,2
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COMMENT
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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
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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
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G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2
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CROSSREFS
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Sequence in context: A132832 A079116 A109222 this_sequence A052956 A008930 A164362
Adjacent sequences: A006858 A006859 A006860 this_sequence A006862 A006863 A006864
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KEYWORD
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nonn
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AUTHOR
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Simon Plouffe, N. J. A. Sloane (njas(AT)research.att.com).
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