A051569 Consider the problem of placing N = A051756(n) queens on an n X n board so that each queen attacks precisely 3 others; a(n) gives the number of inequivalent solutions.

1, 2, 4, 31, 304, 2, 9, 755, 39302

Offset: 2

Author

N. J. A. Sloane

Keywords

• nonn
• more

References

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

Crossrefs

Cf. A051567-A051571, A051754-A051759, A019654.

Extensions

I am not certain this description is correct, nor how rigorous the results are. Probably this is an incorrect version of A051759.