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A322536
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Number of arrays of 9 integers in -n..n with sum zero.
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2
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1, 3139, 180325, 2636263, 19610233, 97464799, 370487485, 1163205475, 3164588407, 7702189345, 17148949027, 35500063501, 69161990275, 128000343121, 226698100687, 386480229085, 637265493637, 1020310909975, 1591418959705, 2424782370859, 3617545938373, 5295169534843
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = [x^(9*n)] (Sum_{k=0..2*n} x^k)^9.
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MATHEMATICA
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a[n_] := Coefficient[Expand[Sum[x^k, {k, 0, 2n}]^9, x], x, 9n]; Array[a, 25, 0] (* Amiram Eldar, Dec 14 2018 *)
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PROG
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(PARI) {a(n) = polcoeff((sum(k=0, 2*n, x^k))^9, 9*n, x)}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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