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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. 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Permutations of the 3 points are not counted separately.

LINKS

Giovanni Resta, Table of n, a(n) for n = 1..100

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.

Cf. A115004, A320544.

Sequence in context: A038607 A079009 A097651 * A059673 A294152 A196701

Adjacent sequences:  A320537 A320538 A320539 * A320541 A320542 A320543

KEYWORD

nonn

AUTHOR

Hugo Pfoertner, Oct 15 2018

EXTENSIONS

a(27)-a(40) from Giovanni Resta, Oct 26 2018

STATUS

approved

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Last modified November 22 08:46 EST 2019. Contains 329389 sequences. (Running on oeis4.)