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A104454
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Expansion of 1/(sqrt(1-5x)*sqrt(1-9x)).
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11
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1, 7, 51, 385, 2995, 23877, 194109, 1602447, 13389075, 112935445, 959783881, 8206116387, 70507643101, 608271899515, 5265458413875, 45711784088145, 397829544860115, 3469772959954245, 30319709631711225, 265383615634224675, 2326318766651511945, 20419439617056272415
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OFFSET
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0,2
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COMMENTS
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Fifth binomial transform of A000984. In general, the k-th binomial transform of A000984 will have g.f. 1/(sqrt(1-k*x)*sqrt(1-(k+4)*x)) and a(n)=sum{i=0..n, C(n,i)C(2i,i)k^(n-i)}.
Diagonal of rational function 1/(1 - (x^2 + 7*x*y + y^2)). - Gheorghe Coserea, Aug 03 2018
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LINKS
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FORMULA
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G.f.: 1/sqrt(1-14*x+45*x^2).
E.g.f.: exp(7x)*BesselI(0, 2x)
a(n) = Sum_{k=0..n} 5^(n-k)*binomial(n,k)*binomial(2k,k).
D-finite with recurrence: n*a(n) = 7*(2*n-1)*a(n-1) - 45*(n-1)*a(n-2). - Vaclav Kotesovec, Oct 17 2012
a(n) = Sum_{k=0..n} 9^(n-k) * (-1)^k * binomial(n,k) * binomial(2*k,k). - Seiichi Manyama, Apr 22 2019
a(n) = Sum_{k=0..floor(n/2)} 7^(n-2*k) * binomial(n,2*k) * binomial(2*k,k). - Seiichi Manyama, May 04 2019
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MATHEMATICA
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CoefficientList[Series[1/(Sqrt[1-5x] Sqrt[1-9x]), {x, 0, 30}], x] (* Harvey P. Dale, Apr 11 2012 *)
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PROG
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(PARI) x='x+O('x^66); Vec(1/sqrt(1-14*x+45*x^2)) \\ Joerg Arndt, May 13 2013
(PARI) {a(n) = sum(k=0, n, 9^(n-k)*(-1)^k*binomial(n, k)*binomial(2*k, k))} \\ Seiichi Manyama, Apr 22 2019
(PARI) {a(n) = sum(k=0, n\2, 7^(n-2*k)*binomial(n, 2*k)*binomial(2*k, k))} \\ Seiichi Manyama, May 04 2019
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CROSSREFS
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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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