

A175383


Number of complete quadrangles on an n X n grid (or geoplane).


9



0, 1, 78, 1278, 9498, 47331, 175952, 545764, 1461672, 3507553, 7701638, 15773526, 30375194, 55695587, 97777392, 165310348, 270478344, 430196181, 666685134, 1010083690, 1498720098, 2182544223
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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



FORMULA



EXAMPLE

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



EXTENSIONS

a(7)a(22) corrected by Nathaniel Johnston, based on another correction by Michal Forišek, Sep 06 2011


STATUS

approved



