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A169776 Number of geometrically distinct open knight's tours of a 3 X n chessboard that have twofold symmetry. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A165664 A019263 A244132 * 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

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Last modified April 20 22:22 EDT 2019. Contains 322310 sequences. (Running on oeis4.)