0,4

Number of ways to choose 4 points forming a regular tetrahedron out of the binomial(n+2,3) points in a regular tetrahedral grid.

The tetrahedra defined by the four points may have any orientation.

Similar to A216173, which differs from the present sequence in a mysterious way.

Table of n, a(n) for n=0..44.

It would be nice to have a g.f. - N. J. A. Sloane, Mar 21 2016

Cf. A000332 (2-D version), A216173, A270805, A270806.

Sequence in context: A082190 A155965 A216173 * A011863 A027085 A099452

Adjacent sequences: A269744 A269745 A269746 * A269748 A269749 A269750

nonn

Warren D. Smith, Mar 21 2016; more terms Mar 23 2016

approved