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A054890
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Layer counting sequence for hyperbolic tessellation by regular heptagons of angle Pi/3.
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1, 7, 42, 245, 1428, 8323, 48510, 282737, 1647912, 9604735, 55980498, 326278253, 1901689020, 11083855867, 64601446182, 376524821225, 2194547481168, 12790760065783, 74550012913530, 434509317415397
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The layer sequence is the sequence of the cardinalities of the layers accumulating around a (finite-sided) polygon of the tessellation under successive side-reflections; see the illustration accompanying A054888.
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FORMULA
| G.f.: (x^2+x+1)/(x^2-6*x+1)
a(n) = A001109(n) + A001109(n-1) + A001109(n-2), n>1. - Ralf Stephan, Apr 26 2003
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CROSSREFS
| {a(n)/7} for n>1 is A001109.
Sequence in context: A111995 A050152 A030240 * A102594 A053142 A162941
Adjacent sequences: A054887 A054888 A054889 * A054891 A054892 A054893
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KEYWORD
| nonn
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AUTHOR
| Paolo Dominici (pl.dm(AT)libero.it), May 23 2000
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