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%I #22 Jan 30 2020 21:29:16
%S 1,8,120,2192,44248,949488,21237168,489517344,11544312984,
%T 277190766896,6753051796240,166505875155936,4146984734796016,
%U 104174408364697952,2636346768784492128,67149645964991840832,1720072455615130558488
%N G.f.: 7/(3 + 4*sqrt(1-28*x)).
%C 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
%H G. C. Greubel, <a href="/A130979/b130979.txt">Table of n, a(n) for n = 0..690</a>
%F a(n) = Sum_{k=0..n} A039599(n,k)*7^(n-k). - _Philippe Deléham_, Aug 25 2007
%F a(n) ~ 14*28^n/(9*sqrt(Pi)*n^(3/2)). - _Vaclav Kotesovec_, Jun 29 2013
%F D-finite with recurrence: n*a(n) +2*(-46*n+21)*a(n-1) +896*(2*n-3)*a(n-2)=0. - _R. J. Mathar_, Jan 20 2020
%t CoefficientList[Series[7/(3 + 4*Sqrt[1 - 28*x]), {x,0,50}], x] (* _G. C. Greubel_, Jan 28 2017 *)
%o (PARI) Vec(7/(3 + 4*sqrt(1-28*x)) + O(x^50)) \\ _G. C. Greubel_, Jan 28 2017
%Y Column k=8 of A183135.
%K nonn
%O 0,2
%A _Philippe Deléham_, Aug 23 2007
%E More terms from _Olivier Gérard_, Sep 22 2007
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