A317251 - OEIS

A317251

a(n) is the number of ways to paint the 2^n cells of dimension n-1 that bound a regular convex n-orthoplex polytope using exactly 2^n colors where n is the dimension of Euclidean space.

2, 6, 1680, 108972864000, 137047310902965380295426048000000, 5507245320567889066989296412116383715402149139520190633628554443368693760000000000000

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OFFSET

1,1

COMMENTS

Let G, the group of rotations in n-dimensional Euclidean space, act on the set of (2^n)! paintings of an n-orthoplex bound by 2^n cells of dimension n-1. There are (2^n)! fixed points in the action table since the only element in G that leaves a painting fixed is the identity element. The order of G is 2^(n-1)*n! = A002866(n). So by Burnside's Lemma a(n) = (2^n)!/|G|.

See A198861(3) for the number of ways to paint the octahedron a(3) in the Platonic solids and A317978(3) for the 4-orthoplex a(4) in the regular convex 4-polytopes.

LINKS

Frank M Jackson, Table of n, a(n) for n = 1..8

Wikipedia, Cross-polytope

FORMULA

a(n) = (2^n)!/(2^(n-1)*n!) = (2^n)!/A002866(n).

a(n) = 2 * A000723(n). - Alois P. Heinz, Aug 15 2018

MATHEMATICA

a[n_]:=(2^n)!/(2^(n-1)*n!); Array[a, 10]

CROSSREFS

Cf. A000723, A002866, A097801, A198861, A317978.

Sequence in context: A178773 A046857 A129454 * A140258 A071093 A114045

Adjacent sequences: A317248 A317249 A317250 * A317252 A317253 A317254

KEYWORD

nonn

AUTHOR

Frank M Jackson, Aug 13 2018

STATUS

approved