A078603 Number of ways of arranging the numbers 1..n in a circle so that adjacent numbers do not differ by 1 mod n.

1, 0, 0, 0, 2, 6, 46, 354, 3106, 29926, 315862, 3628906, 45132474, 604534846, 8680957902, 133082437730, 2169964347282, 37505486702678, 685046187718022, 13186335387855770, 266816610979894058, 5662225862272325550

Offset

1,5

Links

Table of n, a(n) for n=1..22.

Index entries for sequences related to shoe lacings

Formula

For n>1, a(n) = 2*A002816(n).

Example

a(5) = 2: 1 3 5 2 4, 1 4 2 5 3; a(6) = 6: 1 4 6 2 5 3, 1 5 2 4 6 3, 1 5 3 6 2 4, 1 3 6 4 2 5, 1 4 2 6 3 5, 1 3 5 2 6 4.

Crossrefs

Twice A002816.

The sequence n*a(n) is A089222.

See also A078628.

Sequence in context: A092662 A371341 A052811 * A316073 A001587 A306784

Adjacent sequences: A078600 A078601 A078602 * A078604 A078605 A078606

Keyword

nonn

Author

N. J. A. Sloane, Dec 11 2002

Extensions

The sequence was missing a zero; also added a cross-reference Joel B. Lewis, Jan 28 2010

Status

approved