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A117202
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Binomial transform of n*F(n).
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3
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0, 1, 4, 15, 52, 170, 534, 1631, 4880, 14373, 41810, 120406, 343884, 975325, 2749852, 7713435, 21540304, 59917826, 166094370, 458998523, 1264919720, 3477182961, 9536877614, 26102772910, 71309161752, 194468551225, 529490287924
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OFFSET
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0,3
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COMMENTS
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Number of acyclic subgraphs of the wheel graph W_n (on n+1 vertices) with exactly n-1 edges. - Emil R. Vaughan, Jun 12 2007
Equivalently, number of two-component spanning forests of the wheel graph W_n (on n+1 vertices). - Harry Richman, Jul 31 2023
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LINKS
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FORMULA
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G.f.: x*(1-2x+2x^2)/(1-3x+x^2)^2.
a(n) = 6*a(n-1)-11*a(n-2)+6*a(n-3)-a(n-4).
a(n) = Sum_{k=0..n} C(n,k)*k*F(k).
a(n) = Sum_{k=1..n} F(2k)*B(2n-2k)*binomial(2n,2k) where F=Fibonacci numbers and B=Bernoulli numbers;
a(n) = n*F(2n-1).
(End)
a(n) = (2^(-1-n)*(-(-5+sqrt(5))*(3+sqrt(5))^n + (3-sqrt(5))^n*(5+sqrt(5)))*n) / 5. - Colin Barker, Feb 26 2017
a(n) = (1/sqrt(5)) * n * (((1 + sqrt(5)) / 2)^(2n-1) - (1 - sqrt(5)) / 2)^(2n-1)). - Harry Richman, Jul 31 2023
a(n) = round((1/sqrt(5)) * n * phi^(2n-1)), where phi = (1+sqrt(5))/2 is the golden ratio A001622. - Harry Richman, Jul 31 2023
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MATHEMATICA
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Table[n Fibonacci[2n-1], {n, 0, 26}] (* or *) Table[Sum[Fibonacci[2k]*BernoulliB[2n-2k]*Binomial[2n, 2k], {k, 1, n}], {n, 0, 26}] (* or *) CoefficientList[Series[x(1-2x+2x^2)/(1-3x+x^2)^2 , {x, 0, 26}], x] (* Indranil Ghosh, Feb 26 2017 *)
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PROG
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(PARI) concat(0, Vec(x*(1-2*x+2*x^2) / (1-3*x+x^2)^2 + O(x^30))) \\ Colin Barker, Feb 26 2017
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CROSSREFS
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Cf. A004146 (number of spanning trees of wheel graph).
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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