OFFSET
1,3
COMMENTS
A complete quadrangle is a set of four points, no three collinear, and the six lines which join them.
Number of ways to arrange 4 indistinguishable points on an n X n square grid so that no three points are collinear at any angle. Column 4 of A194193. - R. H. Hardin, Aug 18 2011
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..55
Eric Weisstein's World of Mathematics, Complete Quadrangle.
EXAMPLE
From R. H. Hardin, Aug 18 2011: (Start)
Some solutions for 3 X 3:
0 1 1 1 1 0 1 0 1 0 1 1 0 0 0 1 1 0 1 1 0
1 0 0 0 0 0 1 0 0 1 1 0 1 1 0 0 0 1 1 0 0
1 0 0 1 0 1 0 0 1 0 0 0 0 1 1 0 1 0 0 1 0
(End)
CROSSREFS
KEYWORD
nonn
AUTHOR
Martin Renner, Apr 19 2011
EXTENSIONS
a(6)-a(22) from Nathaniel Johnston, Apr 25 2011
a(7)-a(22) corrected by Nathaniel Johnston, based on another correction by Michal ForiĊĦek, Sep 06 2011
STATUS
approved