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A054890 Layer counting sequence for hyperbolic tessellation by regular heptagons of angle Pi/3. 0
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; text; internal format)
OFFSET

1,2

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.

LINKS

Table of n, a(n) for n=1..20.

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

CROSSREFS

{a(n)/7} for n>1 is A001109.

Sequence in context: A111995 A050152 A030240 * A102594 A053142 A214941

Adjacent sequences:  A054887 A054888 A054889 * A054891 A054892 A054893

KEYWORD

nonn

AUTHOR

Paolo Dominici (pl.dm(AT)libero.it), May 23 2000

STATUS

approved

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Last modified September 26 12:07 EDT 2020. Contains 337371 sequences. (Running on oeis4.)