Cake number
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Cake_number_with_4_cutting_planes.gif/220px-Cake_number_with_4_cutting_planes.gif)
In mathematics, the cake number, denoted by Cn, is the maximum number of regions into which a 3-dimensional cube can be partitioned by exactly n planes. The cake number is so-called because one may imagine each partition of the cube by a plane as a slice made by a knife through a cube-shaped cake.
The values of Cn for increasing n ≥ 0 are given by 1, 2, 4, 8, 15, 26, 42, 64, 93, …(sequence A000125 in the OEIS)
General formula[]
If n! denotes the factorial, and we denote the binomial coefficients by
and we assume that n planes are available to partition the cube, then the n-th cake number is:[1]
Properties[]
The only cake number which is prime is 2, since it requires to have prime factorisation where is some prime. This is impossible for as we know must be even, so it must be equal to , , , or , which correspond to the cases: (which has only complex roots), (i.e. ), , and .[citation needed]
The cake numbers are the 3-dimensional analogue of the 2-dimensional lazy caterer's sequence. The difference between successive cake numbers also gives the lazy caterer's sequence.[1]
References[]
- ^ Jump up to: a b Yaglom, A. M.; Yaglom, I. M. (1987). Challenging Mathematical Problems with Elementary Solutions. 1. New York: Dover Publications.
External links[]
- Eric Weisstein. "Space Division by Planes". MathWorld. Retrieved January 14, 2021.
- Eric Weisstein. "Cake Number". MathWorld. Retrieved January 14, 2021.
- Mathematical optimization
- Combinatorics stubs