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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

Table of n, a(n) for n=1..9.

Vaclav Kotesovec, Examples

CROSSREFS

Cf. A000170, A000769, A001499, A001501, A058528, A075754, A172544, A172541.

Sequence in context: A047854 A222080 A122708 * 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 April 25 05:57 EDT 2017. Contains 285348 sequences.