A368061 - OEIS

A368061

The number of ways to place one pawn and n+1 nonattacking queens on an n X n chessboard, unchanged by 180-degree rotation.

0, 0, 0, 0, 0, 0, 1, 0, 5, 0, 18, 0, 50, 0, 652, 0, 4260, 0, 25134, 0, 238098, 0, 2492304, 0, 25389294

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OFFSET

1,9

COMMENTS

n must be odd, and the pawn must be in the center.

LINKS

FORMULA

A103330(n) = 8*A103331(n) - 4*a(n).

EXAMPLE

For n=7 the a(7)=1 solution is

. . Q . . . .

. . . . . Q .

. . . Q . . .

Q . . P . . Q

. . . Q . . .

. Q . . . . .

. . . . Q . .

CROSSREFS

A103330 counts all solutions; A103331 counts them with symmetry removed.

KEYWORD

nonn,more

AUTHOR

Don Knuth, Dec 10 2023

STATUS

approved