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A131521
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Expansion of 9/(4 + 5*sqrt(1-36*x)).
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6
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1, 10, 190, 4420, 113950, 3128140, 89608780, 2647358920, 80065458910, 2466432898300, 77115832253380, 2440820453410360, 78053018025315340, 2517915855707814520, 81839894422876183000, 2677554649095487584400
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OFFSET
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0,2
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COMMENTS
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Number of walks of length 2n on the 10-regular tree beginning and ending at some fixed vertex. Hankel transform is A135321. - Philippe Deléham, Feb 25 2009
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LINKS
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FORMULA
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G.f.: 9/(4 + 5*sqrt(1-36*x)).
D-finite with recurrence: n*a(n) +2*(-68*n+27)*a(n-1) +1800*(2*n-3)*a(n-2)=0. - R. J. Mathar, Jan 20 2020
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MATHEMATICA
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CoefficientList[Series[9/(4+5*Sqrt[1-36*x]), {x, 0, 30}], x] (* Harvey P. Dale, Aug 21 2012 *)
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PROG
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(PARI) Vec(9/(4 + 5*sqrt(1-36*x)) + O(x^50)) \\ G. C. Greubel, Jan 28 2017
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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