OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..450
Wikipedia, Multinomial coefficients
Wikipedia, Partition (number theory)
FORMULA
a(n) ~ c * n!, where c = A247551 = 2.5294774720791526481801161542539542411787... - Vaclav Kotesovec, Sep 28 2019
MAPLE
b:= proc(n, i, k) option remember; `if`(n=0, 1,
`if`(i>n, 0, b(n, i+1, `if`(i=k, 0, k))+
`if`(i=k, 0, b(n-i, i, k)*binomial(n, i))))
end:
a:= n-> b(n, 1, 0)-b(n, 1$2):
seq(a(n), n=0..23);
MATHEMATICA
b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i < 2, 0, b[n, i - 1, If[i == k, 0, k]]] + If[i == k, 0, b[n - i, Min[n - i, i], k]/i!]];
T[n_, k_] := n! (b[n, n, 0] - If[k == 0, 0, b[n, n, k]]);
a[n_] := T[n, 1];
a /@ Range[0, 23] (* Jean-François Alcover, Dec 09 2020, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 26 2019
STATUS
approved