All Questions
20
questions
0
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28
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Number of partitions with limited cardinality [duplicate]
We are given $k$ urns labeled from $1$ to $k$. What is the number of ways to put $n$ indistinguishable balls into the $k$ (distinct) urns, given that each urn has a limited capacity equal to $c$, ...
- 149
1
vote
2
answers
1k
views
The number 3 can be written as $3$, $2+1$, $1+2$ or $1+1+1$ in four ways. In how many ways can the number $n$ be written?
Attempt
Let $x$ be any variable
$X+0=n ; X+Y=n ; X+Y+Z=n ; \dots; X+Y+Z+A+\dots=n$ (sum of n-1 terms); $1+1+1+.......+1=n$ (sum of n terms).
So total number of ways=
$$(n-1) C (1-1)+(n-1) C (2-1)+\...
- 85
10
votes
1
answer
228
views
Unexpected result on the number of permutations with a restriction.
Let $p=(p_1,p_2,\dots,p_n)$ be a weak composition of a positive integer number $n$ into $n$ non-negative integer parts and let $k_i$ be the count of the part $i$ ($i=0,1,2,\dots$) in the composition.
...
- 26.7k
0
votes
1
answer
54
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Applying boundary conditions to counting combinatorial question [duplicate]
I was trying to count the number of natural number solutions to the equation: $x_1 + x_2 + ... + x_{11} = 20$, such that $0 \leq x_i \leq 9$, for all $i \in \{1, ..., 11\}$.
I know how to apply the ...
- 2,663
0
votes
1
answer
194
views
Integer partitions and permutations
I am given the pair $(n, \lambda)$ where $\lambda$ is a partition of $n$ such that 6 is not a part in $\lambda$. I am told to let $\lambda^*$ represent the partition of $n$ conjugate to $\lambda$. ...
- 337
0
votes
0
answers
26
views
Making a group of $p$ people with $n$ available nationalities
Making a group of p people using m out of n available nationalities can be one of these two scenarios;
$m \le p \le n$ or $m \le n \le p$.
Using p,m, and n, how to evaluate the number of ways of ...
- 5,450
1
vote
2
answers
196
views
Limit the maximum value of the composition of an integer
I was doing a coding test (already finished, so no cheating for me) and came across this problem, which I'll describe in few steps:
We have a keypad, like on cellphones, with keys from 1 to 9, where ...
- 111
0
votes
0
answers
70
views
Number of ways to partition $\{1,2,3, \dots, N\}$ into tuples where the size of no tuple exceeds $3$.
While it seems to me that the general answer is not going to be a neat formula, I really only need this for $N=4$ and $N=5$. I'm getting $61$ and $321$ respectively, but I'm not sure. Please help.
- 981
-1
votes
1
answer
89
views
Number of ordered set partitions with subset size $\leq 3$
For $n \ge 0$, let $h_n$ be the number of ways of taking $n$ (distinguishable)
rabbits, putting them into identical cages with one to three rabbits per
cage and then ordering the cages in a row. Find ...
- 434
3
votes
1
answer
852
views
Counting ordered integer partition permutations of max part size
Is there a better way to do this?
The question as it was asked of me was to create an algorithm that counted the total number of ways an integer N could be partitioned into parts of size 6 or less. ...
- 31
2
votes
3
answers
1k
views
Number of ways of cutting a stick such that the longest portion is of length n
We are given a stick of length $L$ (say). We make cuts such that the longest piece is of length $n$ (say) at most.
What are the minimum number of pieces we will get and in how many ways this can be ...
5
votes
1
answer
4k
views
How many permutations in S(n) have this particular type?
I'm working through the textbook A Course in Enumeration. In the section about permutations and Stirling numbers, I'm having trouble understanding problem 1.45. It is:
We fix $n \in \mathbb{N}$, and ...
- 468
2
votes
2
answers
171
views
How many combination of $3$ integers reach given number?
I have 3 numbers
$M=10$
$N=5$
$I=2$
Suppose I have been given number $R$ as input that is equal to $40$
so in how many ways these $3$ numbers arrange them selves to reach $40$
e.g.
$$10+10+10+...
- 23
5
votes
2
answers
360
views
How many numbers of $10$ digits that have at least $5$ different digits are there?
In principle I resolved it as if the first number could be zero, to the end eliminate those that start with zero.
The numbers that can use $4$ certain figures (for example, $1$, $2$, $3$ and $4$) are ...
- 865
0
votes
2
answers
275
views
How many distinct, non-negative integer solutions are there for $2x_0+\sum_{i=1}^{m}{x_i}=n$?
We are given constants $m$ and $n$. How many non-negative integer solutions are there for $2x_0+\sum_{i=1}^{m}{x_i}=n$ satisfying the condition that$x_i\neq x_j$ if $i\neq j$?
I thought a good first ...
- 535