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A032037
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Doubles (index 2+) under "AIJ" (ordered, indistinct, labeled) transform.
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4
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1, 2, 18, 264, 5400, 141840, 4551120, 172529280, 7545363840, 373944211200, 20711190931200, 1267784551756800, 84991791159475200, 6193091146059417600, 487361761916020992000, 41192820513212239872000, 3721763273059549605888000, 357950394802026289815552000
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OFFSET
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1,2
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LINKS
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FORMULA
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E.g.f.: series reversion of x*(1-2*x)/(1-x). - Andrew Howroyd, Sep 19 2018
Assuming offset = 0:
a(n) = Sum_{k=0..n} Sum{m=0..k} (-1)^(m + k) * binomial(n + k, n + m) * binomial(n + m - 1, m - 1) * (n + m)! / m!. - Peter Luschny, Sep 26 2022
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MATHEMATICA
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a[1]=1; a[2]=2; a[n_] := a[n]=3(2n-3)a[n-1]-(n-1)(n-3)a[n-2]
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PROG
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(PARI) Vec(serlaplace(serreverse(x*(1-2*x)/(1-x) + O(x^20)))) \\ Andrew Howroyd, Sep 19 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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