A204841 (2n)! - 2^n*n!.

0, 0, 16, 672, 39936, 3624960, 478955520, 87177646080, 20922779566080, 6402373519933440, 2432902004460748800, 1124000727695858073600, 620448401731277448806400, 403291461126554623829606400, 304888344611712432172380979200, 265252859812191015786434789376000

Offset: 0

Author

Geoffrey Critzer, Jan 19 2012

Keywords

• nonn

Comments

a(n) is the number of ways to seat (linearly order) n married couples so that at least one couple is separated.

Crossrefs

Cf. A007060.

Programs

Mathematica

Table[(2n)! - 2^n n!, {n,0,20}]

Formula

a(n) = A010050(n) - A000165(n).