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A206723 a(n) = 7( ((3+sqrt(5))/2)^n + ((3-sqrt(5))/2)^n - 2). 0
7, 35, 112, 315, 847, 2240, 5887, 15435, 40432, 105875, 277207, 725760, 1900087, 4974515, 13023472, 34095915, 89264287, 233696960, 611826607, 1601782875, 4193522032, 10978783235, 28742827687, 75249699840, 197006271847, 515769115715, 1350301075312, 3535134110235, 9255101255407, 24230169656000, 63435407712607, 166076053481835, 434792752732912 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..33.

Hang Gu and Robert M. Ziff, Crossing on hyperbolic lattices, arXiv preprint arXiv:1111.5626, 2011

Index to sequences with linear recurrences with constant coefficients, signature (4,-4,1).

FORMULA

G.f.: -7*x*(1+x) / ( (x-1)*(x^2-3*x+1) ). - R. J. Mathar, Nov 15 2013

CROSSREFS

Equals 7*A004146 for n >= 1.

Sequence in context: A037092 A210368 A015667 * A124090 A250284 A059595

Adjacent sequences:  A206720 A206721 A206722 * A206724 A206725 A206726

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 11 2012

STATUS

approved

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Last modified November 29 01:24 EST 2014. Contains 250479 sequences.