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A006770
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Number of fixed n-celled polyominoes which need only touch at corners.
(Formerly M3565)
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13
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1, 4, 20, 110, 638, 3832, 23592, 147941, 940982, 6053180, 39299408, 257105146, 1692931066, 11208974860, 74570549714, 498174818986, 3340366308393
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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Also known as fixed polyplets. - David Bevan, Jul 28 2009
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REFERENCES
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D. H. Redelmeier, personal communication.
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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Eric Weisstein's World of Mathematics, Polyplet.
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EXAMPLE
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a(2)=4: the two fixed dominoes and the two rotations of the polyplet consisting of two cells touching at a vertex. - David Bevan, Jul 28 2009
a(3)=20 counts 4 rotations (by 0°, 45°, 90°, 135°) of the straight ... trinomino, and 8 rotations (by multiples of 45°) of the L-shaped .: trinomino and the ..· 3-polyplet, cf. link to the image. - M. F. Hasler, Sep 30 2014
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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