A051567 Consider problem of placing N queens on an n X n board so that each queen attacks precisely k others. Here k=1 and sequence gives number of inequivalent solutions when N is equal to the upper bound 2*floor(2n/3).

0, 5, 0, 2, 149, 49, 1, 12897, 2238

Offset: 3

Author

N. J. A. Sloane

Keywords

• nonn
• more
• nice

Comments

a(n) = 0 if N does not achieve 2*floor(2n/3).

References

• M. Gardner, The Last Recreations, Springer, 1997, p. 282.
• M. Gardner, The Colossal Book of Mathematics, 2001, p. 209.

Links

• Martin Gardner, The Last Recreations, 1997
• Vaclav Kotesovec, The unique solution for chessboard 9 X 9
• Manfred Scheucher, C Code

Crossrefs

Cf. A051568-A051571, A051754-A051759, A019654.

The number of solutions when N takes its maximal value is A051757.

Extensions

Description corrected by and one more term from Jud McCranie, Aug 25 2001