Cells n | distinct | distinct | identical | identical |
---|
Balls k | distinct | identical | distinct | identical |
0≤xi≤1, n≥k | (n−k)!n!=(n)k | (kn) | 1 | 1 |
xi≥0 | nk | (kn+k−1) | | p(k) ^[Partition] |
xi≥1 | n!{nk} | (n−1k−1) | | pn(k) ^[ [[Partition#Partition into k]]. Note, there, n is balls, and k is cells ] |
Shahriari, An Invitation to Combinatorics, 349.
# | k Balls | n Cells | Order in Cell | Empty Cells | Additional Restrictions | Formula / Notation |
---|
1 | Identical | Distinct | No | allowed | At most 1 per cell | (kn) if k≤n |
2 | Distinct | Distinct | No | allowed | At most 1 per cell | (kn)⋅k! if k≤n |
3 | Distinct | Distinct | No | allowed | None | nk |
4 | Identical | Distinct | No | allowed | None | (kn+k−1) |
5 | Distinct | Distinct | Yes | allowed | None | nk |
6 | Distinct | Distinct | No | Not allowed | None | S(k,n)⋅n! |
7 | Distinct | Identical | No | Not allowed | None | S(k,n) |
8 | Distinct | Distinct | No | Not allowed | Any number of cells | ∑i=1nS(k,i)⋅(in)⋅i! |
9 | Distinct | Identical | No | Not allowed | Any number of cells | ∑i=1nS(k,i) |
10 | Identical | Identical | No | Not allowed | None | pn(k) (partitions of k into exactly n positive integers) |
11 | Identical | Identical | No | Not allowed | Any number of cells | p(k) (all integer partitions of k) |