A169776 Number of geometrically distinct open knight's tours of a 3 X n chessboard that have twofold symmetry.

2, 0, 0, 2, 10, 12, 22, 60, 76, 160, 292, 652, 1148, 2600, 3870, 9152, 13710, 32792, 48112, 116624, 171732, 428064, 589842, 1496508, 2069766, 5348640, 7164172, 18742712, 25160796, 66758832, 86664762, 232553036, 302742306, 821495496, 1044549008

Offset

4,1

References

D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010.

Links

Table of n, a(n) for n=4..38.

George Jelliss, Open knight's tours of three-rank boards, Knight's Tour Notes, note 3a (21 October 2000).

George Jelliss, Closed knight's tours of three-rank boards, Knight's Tour Notes, note 3b (21 October 2000).

D. E. Knuth Generating functions for A169770-A169777 and A169696.

Formula

A169776(n) = (A169773(n) + A169774(n) + A169775(n))/2.

Crossrefs

Cf. A070030, A169696, A169764-A169777.

Sequence in context: A244132 A337615 A330607 * A240766 A265494 A091731

Adjacent sequences: A169773 A169774 A169775 * A169777 A169778 A169779

Keyword

nonn

Author

N. J. A. Sloane, May 10 2010, based on a communication from Don Knuth, Apr 28 2010

Extensions

a(31)-a(38) from Andrew Howroyd, Jul 01 2017

Status

approved