A204841 - OEIS

A204841

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

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

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OFFSET

0,3

COMMENTS

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

LINKS

Table of n, a(n) for n=0..15.

FORMULA

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

MATHEMATICA

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

CROSSREFS