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 A225623 Number of ways to arrange 2n queens on an n X n chessboard, with no more than 2 queens in each row, column or diagonal. 2
 0, 1, 2, 11, 92, 1097, 19448, 477136, 14244856 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS This problem is slightly different from A000769 or A219760. In the first example on an 8 x 8 board, are the queens c7, d5 and e3 (or queens a2, c5 and e8) in a line, but such case is allowed. The elementary step can be only [0,1], [1,0] or [1,1], not for example [1,2] or [2,3]. LINKS Vaclav Kotesovec, Examples CROSSREFS Cf. A000170, A000769, A001499, A001501, A058528, A075754, A172544, A172541. Sequence in context: A222080 A122708 A292424 * A005366 A068392 A164893 Adjacent sequences:  A225620 A225621 A225622 * A225624 A225625 A225626 KEYWORD nonn,more,hard AUTHOR Vaclav Kotesovec, Aug 04 2013 EXTENSIONS Definition clarified by Vaclav Kotesovec, Dec 18 2014 STATUS approved

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Last modified August 17 03:29 EDT 2018. Contains 313810 sequences. (Running on oeis4.)