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A320540
(1/4) * number of ways to select 3 distinct collinear points from a square of grid points with side length n.
8
0, 2, 11, 38, 93, 206, 386, 678, 1112, 1748, 2583, 3768, 5253, 7172, 9630, 12720, 16370, 20910, 26169, 32566, 40139, 48962, 58900, 70710, 84096, 99284, 116469, 136116, 157671, 182436, 209436, 239596, 272976, 309630, 350035, 395346, 444021, 496890, 554402, 617906
OFFSET
1,2
COMMENTS
Permutations of the 3 points are not counted separately.
LINKS
EXAMPLE
a(2) = 2 because there are 8 triples of collinear points in the square [0 2] X [0 2]: The 2*3 lines of x=0,1,2 and y=0,1,2 and the 2 diagonals.
CROSSREFS
(1/2)* diagonal of triangle A320539.
Sequence in context: A038607 A079009 A097651 * A059673 A294152 A196701
KEYWORD
nonn
AUTHOR
Hugo Pfoertner, Oct 15 2018
EXTENSIONS
a(27)-a(40) from Giovanni Resta, Oct 26 2018
STATUS
approved