A353884 Expansion of e.g.f. 1/(1 - (x * (exp(x) - 1))^3 / 36).
1, 0, 0, 0, 0, 0, 20, 210, 1400, 7560, 36120, 159390, 1035100, 17082780, 329893564, 5336661330, 73265956400, 889068944400, 9968073461616, 112902000191334, 1531070090032500, 27610559023112100, 586336131631313140, 12550716321612658266, 254052845940651258600
Offset: 0
Keywords
Programs
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PARI
my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-(x*(exp(x)-1))^3/36))) -
PARI
a(n) = n!*sum(k=0, n\6, (3*k)!*stirling(n-3*k, 3*k, 2)/(36^k*(n-3*k)!));
Formula
a(n) = n! * Sum_{k=0..floor(n/6)} (3*k)! * Stirling2(n-3*k,3*k)/(36^k * (n-3*k)!).