A103657 Number of different volumes assumed by triangular pyramids with their 4 vertices chosen from distinct points of an (n+1)X(n+1)X(n+1) lattice cube, including degenerate objects with volume=0.

3, 13, 39, 90, 178, 309, 503, 756, 1096, 1523, 2059, 2683, 3469, 4355, 5406

Offset

1,1

Links

Table of n, a(n) for n=1..15.

Example

a(1)=3 because 4-point objects with 3 different volumes can be built using the vertices of a cube: 2 regular tetrahedra (e.g. [(0,0,0),(0,1,1),(1,0,1),(1,1,0)]) with volume 1/3, 56 pyramids with volume 1/6 and 12 objects with volume=0, e.g. the faces of the cube.
a(2)=13: The A103157(2)=17550 4-point objects that can selected from the 27 points of a 3X3X3 lattice cube fall into 13 different volume classes (6*V,occurrences):
(0,2918), (1,3688), (2,5272), (3,1272), (4,2788), (5,272), (6,684), (7,72), (8,494), (9,16), (10,48), (12,24), (16,2).
A103658(n) gives the occurrence counts of objects with V=0 (i.e. A103658(2)=2918).
A103659(n) gives 6*V of the most frequently occurring volume and A103660(n) gives the corresponding occurrence count, divided by 2. Therefore A103659(2)=2 and A103660(2)=2636.
A103661(n) gives the smallest value of 6*V not occurring in the list of 4-point object volumes, i.e. A103661(2)=11.

Crossrefs

Cf. A103157 binomial((n+1)^3, 4), A103158 tetrahedra in lattice cube, A103656, A103658, A103659, A103660, A103661.

Sequence in context: A323009 A328703 A166911 * A320661 A122504 A103277

Adjacent sequences: A103654 A103655 A103656 * A103658 A103659 A103660

Keyword

hard,nonn

Author

Hugo Pfoertner, Feb 17 2005

Status

approved