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A002013
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Filaments with n square cells.
(Formerly M0835 N0317)
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9
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1, 1, 1, 2, 3, 7, 13, 31, 65, 154, 347, 824, 1905, 4512, 10546, 24935, 58476, 138002, 323894, 763172, 1790585, 4213061, 9878541, 23214728, 54393063, 127687369, 298969219, 701171557, 1640683309, 3844724417, 8991137036, 21054243655, 49211076053
(list;
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refs;
listen;
history;
text;
internal format)
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OFFSET
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0,4
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COMMENTS
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Or, number of 2-sided snake polyominoes with n cells. - Ed Pegg Jr, May 13 2009
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REFERENCES
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N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. C. Tilley, R. G. Stanton and D. D. Cowan, The cell growth problem for filaments, pp. 310-339 in Proceedings of the Louisiana Conference on Combinatorics, Graph Theory and Computer Science. Vol. 1, edited R. C. Mullin et al., 1970.
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LINKS
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Eric Weisstein's World of Mathematics, Polyomino
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CROSSREFS
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A333313 counts 2-sided (free) "strip" polyominoes; that is, snakes with no holes.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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