OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..447
Wikipedia, Permutation
FORMULA
E.g.f.: (1-exp(-x))/(1-x)^4.
a(n) = -1/3! * Sum_{j=1..n} (-1)^j * binomial(n,j) * (n+3-j)!.
a(n) = A306234(n+3,3).
MAPLE
a:= n-> (k-> -add((-1)^j*binomial(n, j)*(n+k-j)!, j=1..n)/k!)(3):
seq(a(n), n=0..23);
MATHEMATICA
m = 23;
CoefficientList[(1-Exp[-x])/(1-x)^4 + O[x]^(m+1), x]*Range[0, m]! (* Jean-François Alcover, May 03 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 23 2019
STATUS
approved