OFFSET
7,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 7..200
FORMULA
a(n) ~ (7*exp(363/140) - 6*exp(49/20)) * n^(n-1). - Vaclav Kotesovec, Aug 21 2014
MAPLE
with(combinat):
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
add((i-1)!^j*multinomial(n, n-i*j, i$j)/j!*
b(n-i*j, i-1), j=0..n/i)))
end:
A:= (n, k)-> add(binomial(n-1, j-1)*n^(n-j)*b(j, min(j, k)), j=0..n):
a:= n-> A(n, 7) -A(n, 6):
seq(a(n), n=7..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 19 2014
STATUS
approved