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A235454 Number of non-equivalent (mod D_4) ways to arrange 3 points on an n X n square grid so that they are not collinear. 6
1, 13, 70, 290, 867, 2266, 5068, 10475, 19764, 35406, 59817, 97375, 152154 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,2
COMMENTS
Column 3 of A235453.
Also number of non-equivalent triangles in an n X n grid.
Without the restriction "non-equivalent (mod D_4)" the numbers are given by A045996, n >= 2.
LINKS
EXAMPLE
There are a(3) = 13 non-equivalent ways to place 3 points on a 3 X 3 grid:
. . . . . . X . . . X . . . . . X . . X .
X . . X . . . . . . . . . X . X . X X X .
X X . X . X X . X X . X X . X . . . . . .
-
. . . . . . . . . . X . . X . . . X
X . X . X X X X . . . X X . . X . .
X . . X . . X . . X . . X . . X . .
CROSSREFS
Cf. A235453, A045996, A235455 (4 points), A235456 (5 points), A235457 (6 points), A235458 (7 points).
Sequence in context: A085461 A081860 A050403 * A296831 A031442 A066831
KEYWORD
nonn,more
AUTHOR
Heinrich Ludwig, Jan 12 2014
EXTENSIONS
a(13), a(14) from Heinrich Ludwig, Nov 16 2016
STATUS
approved

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Last modified June 14 01:54 EDT 2024. Contains 373391 sequences. (Running on oeis4.)