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.

0, 1, 2, 11, 92, 1097, 19448, 477136, 14244856, 537809179, 24194010708, 1317062528249

Offset

1,3

Comments

This problem is slightly different from A000769 or A219760. In the first example on an 8 x 8 board, the queens c7, d5 and e3 (or queens a2, c5 and e8) are 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..12.

Vaclav Kotesovec, Examples

Crossrefs

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

Sequence in context: A337012 A322767 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

a(10)-a(12) from Martin Ehrenstein, Jan 09 2022

Status

approved