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A343687
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a(0) = 1; a(n) = 4 * n * a(n-1) + Sum_{k=0..n-1} binomial(n,k) * (n-k-1)! * a(k).
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2
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1, 5, 51, 782, 15992, 408814, 12541010, 448834728, 18358297416, 844755218400, 43190363326992, 2429044756967520, 149029669269441456, 9905401062535389072, 709016063545908259248, 54375505616232613595904, 4448148376192382963462400, 386619861956492109750650496, 35580548688887294090357622912
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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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E.g.f.: 1 / (1 - 4*x + log(1 - x)).
a(n) ~ n! / ((4/c + 3 - c) * (1 - c/4)^n), where c = LambertW(4*exp(3)) = 3.2176447220005493578369738... - Vaclav Kotesovec, Apr 26 2021
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MATHEMATICA
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a[0] = 1; a[n_] := a[n] = 4 n a[n - 1] + Sum[Binomial[n, k] (n - k - 1)! a[k], {k, 0, n - 1}]; Table[a[n], {n, 0, 18}]
nmax = 18; CoefficientList[Series[1/(1 - 4 x + Log[1 - x]), {x, 0, nmax}], x] Range[0, nmax]!
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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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