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A182666
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E.g.f.: Product_{n>=1} Sum_{k>=0} (x^k/k!)^n.
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1
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1, 1, 3, 13, 67, 471, 3591, 33573, 329043, 3919387, 47827093, 663429603, 9764977399, 156308277139, 2653548775671, 48880554540093, 934560430625523, 19120475459863299, 413057291727064689, 9325822483756554831, 221409989926026560757, 5513060361601128645777
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OFFSET
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0,3
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LINKS
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EXAMPLE
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E.g.f.: A(x) = 1 + x + 3*x^2/2! + 13*x^3/3! + 67*x^4/4! + 471*x^5/5! + 3591*x^6/6! +...
where
A(x) = [Sum_{k>=0} x^k/k!] * [Sum_{k>=0} (x^k/k!)^2] * [Sum_{k>=0} (x^k/k!)^3] * [Sum_{k>=0} (x^k/k!)^4] *...
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MAPLE
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b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0, add(
b(n-i*j, i-1)*combinat[multinomial](n, n-i*j, j$i), j=0..n/i)))
end:
a:= n-> b(n$2):
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MATHEMATICA
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multinomial[n_, k_List] := n!/Times @@ (k!);
b[n_, i_] := b[n, i] = If[n == 0, 1, If[i < 1, 0, Sum[b[n - i*j, i - 1]* multinomial[n, Join[{n - i*j}, Table[j, {i}]]], {j, 0, n/i}]]];
a[n_] := b[n, n];
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PROG
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(PARI) {a(n)=n!*polcoeff(prod(m=1, n, sum(k=0, n\m+1, x^(m*k)/k!^m)+x*O(x^n)), n)}
for(n=0, 30, print1(a(n), ", "))
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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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