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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 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). 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.)