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A107396
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a(n) = binomial(n+5, 5) * binomial(n+7, 5).
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1
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21, 336, 2646, 14112, 58212, 199584, 594594, 1585584, 3864861, 8744736, 18582564, 37425024, 71954064, 132838272, 236618172, 408282336, 684723501, 1119300336, 1787771370, 2795913120, 4289184900, 6464858400, 9587091150, 14005489680, 20177780805, 28697288256
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OFFSET
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0,1
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (11,-55,165,-330,462,-462,330,-165,55,-11,1).
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FORMULA
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Sum_{n>=0} 1/a(n) = 350*Pi^2/3 - 82901/72.
Sum_{n>=0} (-1)^n/a(n) = 1975/24 - 25*Pi^2/3. (End)
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EXAMPLE
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If n=0 then C(0+5,5)*C(0+7,5) = C(5,5)*C(7,5) = 1*21 = 21.
If n=9 then C(6+5,5)*C(6+7,5) = C(11,5)*C(13,5) = 462*1287 = 594594.
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MATHEMATICA
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a[n_] := Binomial[n + 5, 5] * Binomial[n + 7, 5]; Array[a, 25, 0] (* Amiram Eldar, Sep 01 2022 *)
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PROG
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(PARI) a(n)={binomial(n+5, 5) * binomial(n+7, 5)} \\ Andrew Howroyd, Nov 08 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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EXTENSIONS
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a(7) corrected and terms a(15) and beyond from Andrew Howroyd, Nov 08 2019
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STATUS
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approved
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