OFFSET
0,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..27
Wikipedia, Partition of a set
FORMULA
EXAMPLE
a(1) = 1: 1.
a(2) = 1: 12|34.
a(3) = 28: 123|456|789, 123|457|689, 123|458|679, 123|459|678, 123|467|589, 123|468|579, 123|469|578, 123|478|569, 123|479|568, 123|489|567, 124|356|789, 125|346|789, 126|345|789, 127|389|456, 128|379|456, 129|378|456, 134|256|789, 135|246|789, 136|245|789, 137|289|456, 138|279|456, 139|278|456, 145|236|789, 146|235|789, 156|234|789, 178|239|456, 179|238|456, 189|237|456.
MAPLE
a:= n-> add((-1)^(n-j+1)*binomial(n, j)*(n*j)!/(j!*n!^j), j=0..n-1):
seq(a(n), n=0..10);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 16 2024
STATUS
approved