OFFSET
2,1
COMMENTS
a(n) <= 2[(6n-2)/5]. - Jud McCranie, Aug 12 2001
Conjecture: a(n) = 2[(6n-2)/5] for n >= 2; verified up to n = 100. - Alexander D. Healy, Feb 11 2024
REFERENCES
Martin Gardner, The Last Recreations, Copernicus, NY, 1997, 274-283.
Peter Hayes, A Problem of Chess Queens, Journal of Recreational Mathematics, Baywood, 24(4), 1992, 264-271.
LINKS
Alexander D. Healy, Examples of optimal placements for n <= 61
EXAMPLE
Examples from R. J. Mathar, May 01 2006: (Start)
==== n = 3
6 queens:
Q Q Q
Q - -
Q - Q
6 queens:
Q Q Q
- - -
Q Q Q
==== n = 4
8 queens:
Q Q Q Q
Q - - -
Q - - -
Q - - Q
8 queens:
Q Q Q Q
Q - - -
- - Q -
Q - - Q
8 queens:
Q Q Q Q
- - - -
- - - -
Q Q Q Q
8 queens:
Q Q - Q
- Q - -
- - Q -
Q - Q Q
==== n = 7
16 queens:
Q Q Q - Q - Q
- - - - - - Q
- - - Q - - -
Q - - - - - Q
- - - Q - - -
Q - - - - - -
Q - Q - Q Q Q
16 queens:
Q Q Q - - Q Q
- - - Q - - -
- - - - - - Q
Q - - - - - Q
Q - - - - - -
- - - Q - - -
Q Q - - Q Q Q
(End)
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
Robert Trent (trentrd(AT)hotmail.com), Aug 23 2000
EXTENSIONS
More terms from Jud McCranie, Aug 12 2001
a(10)-a(61) from Alexander D. Healy, Feb 11 2024
STATUS
approved