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A130979 G.f.: 7/(3 + 4*sqrt(1-28*x)). 6
1, 8, 120, 2192, 44248, 949488, 21237168, 489517344, 11544312984, 277190766896, 6753051796240, 166505875155936, 4146984734796016, 104174408364697952, 2636346768784492128, 67149645964991840832, 1720072455615130558488 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Number of walks of length 2n on the 8-regular tree beginning and ending at some fixed vertex. Hankel transform is A135315. - Philippe Deléham, Feb 25 2009

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..690

FORMULA

a(n) = Sum_{k=0..n} A039599(n,k)*7^(n-k). - Philippe Deléham, Aug 25 2007

a(n) ~ 14*28^n/(9*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 29 2013

MATHEMATICA

CoefficientList[Series[7/(3 + 4*Sqrt[1 - 28*x]), {x, 0, 50}], x] (* G. C. Greubel, Jan 28 2017 *)

PROG

(PARI) Vec(7/(3 + 4*sqrt(1-28*x)) + O(x^50)) \\ G. C. Greubel, Jan 28 2017

CROSSREFS

Column k=8 of A183135.

Sequence in context: A165231 A004381 A166179 * A239226 A133308 A191098

Adjacent sequences:  A130976 A130977 A130978 * A130980 A130981 A130982

KEYWORD

nonn

AUTHOR

Philippe Deléham, Aug 23 2007

EXTENSIONS

More terms from Olivier Gérard, Sep 22 2007

STATUS

approved

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Last modified October 20 20:20 EDT 2018. Contains 316402 sequences. (Running on oeis4.)