OFFSET
4,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 4..576
Wikipedia, Partition of a set
MAPLE
b:= proc(n, i, t) option remember; `if`(n=0, [1, 0], `if`(i<1, 0,
add((p-> p+`if`(t>0 and t-j<1, [0, p[1]*i], 0))(
combinat[multinomial](n, i$j, n-i*j)/j!*
b(n-i*j, min(n-i*j, i-1), max(0, t-j))), j=0..n/i)))
end:
a:= n-> b(n$2, 4)[2]:
seq(a(n), n=4..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 06 2020
STATUS
approved