OFFSET
3,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 3..450
Andrew V. Sills, Integer Partitions Probability Distributions, arXiv:1912.05306 [math.CO], 2019.
Wikipedia, Permutation
FORMULA
a(n) = Sum_{k=0..n-2} k * A350016(n,k). - Alois P. Heinz, Dec 12 2021
MAPLE
b:= proc(n, i, t) option remember; `if`(n=0, [1, 0], `if`(i>n, 0,
add((p-> p+`if`(t>0 and t-j<1, [0, p[1]*i], 0))((i-1)!^j*
b(n-i*j, i+1, max(0, t-j))/j!*combinat[multinomial]
(n, i$j, n-i*j)), j=0..n/i)))
end:
a:= n-> b(n, 1, 3)[2]:
seq(a(n), n=3..22);
MATHEMATICA
multinomial[n_, k_List] := n!/Times @@ (k!);
b[n_, i_, t_] := b[n, i, t] = If[n == 0, {1, 0}, If[i > n, 0, Sum[Function[ p, p + If[p =!= 0 && t > 0 && t - j < 1, {0, p[[1]]*i}, {0, 0}]][(i - 1)!^j*b[n - i*j, i + 1, Max[0, t - j]]/j!*multinomial[n, Append[Array[i&, j], n - i*j]]], {j, 0, n/i}]]];
a[n_] := b[n, 1, 3][[2]];
a /@ Range[3, 22] (* Jean-François Alcover, Apr 21 2020, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 02 2020
STATUS
approved