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Search: id:A006770
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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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+0
3
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| 1, 4, 20, 110, 638, 3832, 23592, 147941, 940982, 6053180, 39299408, 257105146, 1692931066, 11208974860, 74570549714, 498174818986, 3340366308393
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Also known as fixed polyplets [From David Bevan (dbevan(AT)emtex.com), Jul 28 2009]
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
D. H. Redelmeier, personal communication.
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LINKS
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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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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 [From David Bevan (dbevan(AT)emtex.com), Jul 28 2009]
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CROSSREFS
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Cf. A030222 (free polyplets) [From David Bevan (dbevan(AT)emtex.com), Jul 28 2009]
Sequence in context: A020084 A026127 A153295 this_sequence A158827 A026156 A025183
Adjacent sequences: A006767 A006768 A006769 this_sequence A006771 A006772 A006773
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KEYWORD
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nonn,hard
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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One more term from Joseph Myers (jsm(AT)polyomino.org.uk), Sep 26 2002
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