A051757 Consider problem of placing A051754(n) queens on an n X n board so that each queen attacks precisely 1 other. Sequence gives number of solutions up to square symmetry.

2, 7, 5, 93, 2, 149, 49, 1, 12897, 2238

Offset: 2

Author

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

Keywords

• nonn
• nice

Comments

When n is a multiple of 3, the bound of 2[2n/3] queens is so tight that in solutions with that number of queens, all attacks must be along rows or columns, making solutions rare. - Jud McCranie

References

• Martin Gardner, The Last Recreations, Copernicus, 1997, 274-283.

Crossrefs

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

Extensions

More terms from Jud McCranie, Aug 14 2001