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>n, 0,
add((p-> p+`if`(t>0 and t-j<1, [0, p[1]*i], 0))(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, 4)[2]:
seq(a(n), n=4..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Mar 03 2020
STATUS
approved