A325010 Triangle read by rows: T(n,k) is the number of chiral pairs of colorings of the facets of a regular n-dimensional orthotope using exactly k colors. Row n has 2n columns.

0, 1, 0, 0, 3, 3, 0, 0, 1, 16, 30, 15, 0, 0, 0, 15, 135, 330, 315, 105, 0, 0, 0, 6, 222, 1581, 4410, 5880, 3780, 945, 0, 0, 0, 1, 205, 3760, 23604, 71078, 116550, 107100, 51975, 10395, 0, 0, 0, 0, 120, 5715, 73755, 427260, 1351980, 2552130, 2962575, 2079000, 810810, 135135

Offset: 1

Author

Robert A. Russell, May 27 2019

Keywords

• nonn
• tabf
• easy

Comments

Also called hypercube, n-dimensional cube, and measure polytope. For n=1, the figure is a line segment with two vertices. For n=2 the figure is a square with four edges. For n=3 the figure is a cube with six square faces. For n=4, the figure is a tesseract with eight cubic facets. The Schläfli symbol, {4,3,...,3}, of the regular n-dimensional orthotope (n>1) consists of a four followed by n-2 threes. Each of its 2n facets is an (n-1)-dimensional orthotope. The chiral colorings of its facets come in pairs, each the reflection of the other.

Also the number of chiral pairs of colorings of the vertices of a regular n-dimensional orthoplex using exactly k colors.

Examples

			The triangle begins with T(1,1):
 0 1
 0 0 3  3
 0 0 1 16  30   15
 0 0 0 15 135  330   315    105
 0 0 0  6 222 1581  4410   5880    3780     945
 0 0 0  1 205 3760 23604  71078  116550  107100   51975   10395
 0 0 0  0 120 5715 73755 427260 1351980 2552130 2962575 2079000 810810 135135
For T(2,3)=3, the three squares have the two edges with the same color adjacent.
		

Links

• Robert A. Russell, Table of n, a(n) for n = 1..132

Crossrefs

Cf. A325008 (oriented), A325009 (unoriented), A325011 (achiral), A325006 (up to k colors).

Other n-dimensional polytopes: A325018 (orthoplex).

Programs

Mathematica

Table[Sum[Binomial[j-k-1,j]Binomial[Binomial[k-j,2],n],{j,0,k-2}],{n,1,10},{k,1,2n}] // Flatten

Formula

T(n,k) = Sum{j=0..k-2} binomial(j-k-1,j) * binomial(binomial(k-j,2),n).

T(n,k) = A325008(n,k) - A325009(n,k) = (A325008(n,k) - A325011(n,k)) / 2 = A325009(n,k) - A325011(n,k).