login
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, 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
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