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A103872
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a(n) = 3*trinomial(n+1,0) - trinomial(n+2,0).
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2
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0, 2, 2, 6, 12, 30, 72, 182, 464, 1206, 3170, 8426, 22596, 61074, 166194, 454950, 1251984, 3461574, 9611190, 26787378, 74916660, 210178458, 591347988, 1668172842, 4717282752, 13369522250, 37970114702, 108045430902
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OFFSET
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0,2
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COMMENTS
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First differs from A059727 for n = 8.
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LINKS
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MAPLE
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trinomial := n -> simplify(GegenbauerC(n, -n, -1/2)):
a := n -> 3*trinomial(n+1) - trinomial(n+2):
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MATHEMATICA
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Table[(4*2^n (2n + 3)!! (3 Hypergeometric2F1[-2 - n, -1 - n, -3/2 - n, 1/4] - 4 Hypergeometric2F1[-2 - n, -2 - n, -3/2 - n, 1/4]))/(n + 2)!, {n, 0, 20}] (* Vladimir Reshetnikov, May 07 2016 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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