A320542 a(n) is the number of ways to select 3 distinct points forming a triangle of unsigned area = n from a square of grid points with side length n, divided by 4.

0, 2, 12, 33, 74, 258, 294, 661, 1258, 1940, 2044, 5254, 4136, 7738, 12902, 13357, 13142, 29540, 21214, 40816, 50388, 50012, 47680, 101662, 83684, 99690, 140638, 158568, 126720, 282042, 167514, 253779, 318556, 302230, 386186, 579833, 350556, 478058, 629582, 765498

Offset: 1

Author

Hugo Pfoertner, Oct 15 2018

Keywords

• nonn

Comments

Let s(n) be the number of ways to select 3 different points from a square of grid points with side length n such that they form a triangle with absolute area n, then a(n) = s(n)/4. Permutations of the vertices are considered equivalent.

Crossrefs

Cf. A115004, A320310, A320540, A320544.

Extensions

a(35)-a(40) from Giovanni Resta, Oct 26 2018