login
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.
13
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
CROSSREFS
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