A320566 Expansion of e.g.f. exp(x) * Product_{k>=1} 1/(1 - x^k/k!).
1, 2, 6, 23, 110, 617, 4035, 29927, 249926, 2316317, 23674841, 264329177, 3207278255, 42011308653, 591460307157, 8905905152798, 142897741683846, 2433947385964373, 43873382718719949, 834402502632550589, 16699964488044322205, 350869837371828862607, 7721899536993122262447
Offset: 0
Keywords
Links
- Vaclav Kotesovec, Table of n, a(n) for n = 0..440
- N. J. A. Sloane, Transforms
Programs
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Maple
seq(coeff(series(factorial(n)*exp(x)*mul((1-x^k/factorial(k))^(-1),k=1..n),x,n+1), x, n), n = 0 .. 22); # Muniru A Asiru, Oct 15 2018
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Mathematica
nmax = 22; CoefficientList[Series[Exp[x] Product[1/(1 - x^k/k!), {k, 1, nmax}], {x, 0, nmax}], x] Range[0, nmax]! nmax = 22; CoefficientList[Series[Exp[x + Sum[Sum[x^(j k)/(k (j!)^k), {j, 1, nmax}], {k, 1, nmax}]], {x, 0, nmax}], x] Range[0, nmax]! Table[Sum[Binomial[n, k] Total[Apply[Multinomial, IntegerPartitions[k], {1}]], {k, 0, n}], {n, 0, 22}]
Formula
E.g.f.: exp(x + Sum_{k>=1} Sum_{j>=1} x^(j*k)/(k*(j!)^k)).
a(n) = Sum_{k=0..n} binomial(n,k)*A005651(k).
a(n) ~ exp(1) * A247551 * n!. - Vaclav Kotesovec, Jul 21 2019
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