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A169774
Number of open knight's tour diagrams of a 3 X n chessboard that are symmetric under 180-degree rotation and have "type F": the endpoints occur in different columns and agree in color with the cells in the nearest corner.
1
2, 0, 0, 4, 12, 20, 28, 120, 104, 304, 384, 1304, 1680, 4936, 5908, 18304, 21412, 63440, 76920, 233248, 281284, 833720, 990104, 2993016, 3523740, 10485472, 12432392, 37485424, 44184884, 131430320, 154630088, 465106072, 544994604, 1622783328, 1904647128
OFFSET
4,1
REFERENCES
D. E. Knuth, Long and skinny knight's tours, in Selected Papers on Fun and Games, to appear, 2010.
LINKS
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).
CROSSREFS
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