A051759 Consider the problem of placing A051756(n) queens on an n X n board so that each queen attacks precisely 3 others. Sequence gives number of solutions up to square symmetry.

1, 2, 4, 31, 307, 2, 9, 755

Offset

2,2

Comments

A051569 (taken from the Martin Gardner references) is another version of this sequence. - N. J. A. Sloane, May 22 2014

References

M. Gardner, The Last Recreations, Springer, 1997, p. 282.

M. Gardner, The Colossal Book of Mathematics, 2001, p. 209.

Links

Table of n, a(n) for n=2..9.

Erich Friedman, Illustration of initial terms

Sean A. Irvine, Java program (github)

Crossrefs

Cf. A051754-A051758, A051567-A051571, A019654.

Sequence in context: A259115 A051569 A087186 * A051570 A082913 A083205

Adjacent sequences: A051756 A051757 A051758 * A051760 A051761 A051762

Keyword

nonn,nice,more

Author

Robert Trent (trentrd(AT)hotmail.com), Aug 23 2000

Extensions

a(8)-a(9) from Sean A. Irvine, Oct 01 2021

Status

approved