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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

Table of n, a(n) for n=2..14.

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

Adjacent sequences:  A235451 A235452 A235453 * A235455 A235456 A235457

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 December 8 11:03 EST 2021. Contains 349594 sequences. (Running on oeis4.)