A371068 E.g.f. satisfies A(x) = 1 + x*exp(x^3*A(x)^3).
1, 1, 0, 0, 24, 360, 2160, 7560, 241920, 8164800, 145756800, 1736380800, 34488115200, 1416906691200, 46117316044800, 1085696644032000, 26627911620710400, 1054301997805056000, 46867776416068608000, 1726488804870679449600, 58404671366139850752000
Offset: 0
Keywords
Programs
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PARI
a(n) = n!*sum(k=0, n\3, (n-3*k)^k*binomial(3*k+1, n-3*k)/((3*k+1)*k!));
Formula
a(n) = n! * Sum_{k=0..floor(n/3)} (n-3*k)^k * binomial(3*k+1,n-3*k)/( (3*k+1)*k! ).