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A350307
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a(n) is the constant term in the expansion of Product_{j=1..n} (Sum_{k=-j..j} x^k)^n.
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2
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1, 1, 37, 100683, 42935363305, 4440604747662968975, 161247684066768055445081543753, 2819198261291991623302749353791096334609249, 31233334332507494719367656927521237896029724037781845363309
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OFFSET
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0,3
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COMMENTS
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a(n) is the coefficient of x^(n^2 * (n+1)/2) in Product_{j=0..n} (Sum_{k=0..2*j} x^k)^n.
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LINKS
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MATHEMATICA
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a[n_] := Coefficient[Series[Product[Sum[x^k, {k, -j, j}]^n, {j, 1, n}], {x, 0, 0}], x, 0]; Array[a, 9, 0] (* Amiram Eldar, Dec 24 2021 *)
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PROG
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(PARI) a(n) = polcoef(prod(j=1, n, sum(k=-j, j, x^k))^n, 0);
(PARI) a(n) = polcoef(prod(j=1, n, sum(k=0, 2*j, x^k))^n, n^2*(n+1)/2);
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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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