A127888 If X_1,...,X_n is a partition of a 6n-set X into 6-blocks then a(n) is equal to the number of permutations f of X such that f(X_i)<>X_i, (i=1,...n).

0, 478483200, 6401339808768000, 620429964386047303680000, 265250626231132937174895820800000, 371992180902371387782970387300352000000000

Offset

1,2

Links

Table of n, a(n) for n=1..6.

Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

Formula

a(n)=sum((-720)^i*binomial(n,i)*(6*n-6*i)!,i=0..n).

Example

a(5)=265250626231132937174895820800000

Maple

a:=n->sum((-720)^i*binomial(n, i)*(6*n-6*i)!, i=0..n).

Crossrefs

Sequence in context: A260524 A091677 A147717 * A072232 A011523 A172535

Adjacent sequences: A127885 A127886 A127887 * A127889 A127890 A127891

Keyword

nonn

Author

Milan Janjic, Apr 09 2007

Status

approved