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A169775 Number of open knight's tour diagrams of a 3 X n chessboard that are symmetric under 180-degree rotation and have "type B": the endpoints occur in different columns and disagree in color with the cells in the nearest corner. 2
2, 0, 0, 0, 8, 0, 16, 0, 48, 0, 200, 0, 616, 0, 1832, 0, 6008, 0, 19304, 0, 62180, 0, 189580, 0, 615792, 0, 1895952, 0, 6136708, 0, 18699436, 0, 60490008, 0, 184450888, 0, 595959276, 0, 1811054676, 0, 5847417040, 0, 17754996288, 0, 57292227492 (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..48.

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

A169775(n)=0 unless n mod 2 = 0.

CROSSREFS

Cf. A070030, A169696, A169764-A169777.

Sequence in context: A272822 A265663 A107491 * A181502 A223154 A063698

Adjacent sequences:  A169772 A169773 A169774 * A169776 A169777 A169778

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

a(31)-a(48) from Andrew Howroyd, Jul 01 2017

STATUS

approved

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Last modified April 23 13:25 EDT 2019. Contains 322386 sequences. (Running on oeis4.)