A078673 Number of ways of arranging the numbers 1..n in a circle so that there is no consecutive triple i, i+1, i+2 or i, i-1, i-2 (mod n).

1, 1, 0, 2, 6, 38, 247, 1831, 15287, 142199

Offset

1,4

Comments

Arrangement that differ only in the direction in which the cycle is traversed do not count as different.

Links

Table of n, a(n) for n=1..10.

Index entries for sequences related to shoe lacings

Crossrefs

Apart from initial terms, A078628/2.

Sequence in context: A267405 A027322 A085447 * A052841 A275557 A197972

Adjacent sequences: A078670 A078671 A078672 * A078674 A078675 A078676

Keyword

nonn

Author

N. J. A. Sloane, Dec 16 2002

Status

approved