Number of ways of putting $n$ balls into $k$ boxes, with a twist…












1












$begingroup$


Usually, when counting the number of ways in which $n$ balls can be put into $k$ boxes, two cases are considered:




  1. Boxes cannot be empty

  2. Boxes can be empty


Respectively, each of the listed cases has a formula:



$$C_1={n-1choose k-1}$$
$$C_2={n+k-1choose n}$$



This however doesn't suffice my needs. I want the boxes to be all not empty, and be countable, just like in the first case... But I want the boxes to be indistinguishable.



That is, as long as you have 4 balls in box 1, 2 balls in box 2, and 1 ball in box 3, it doesn't matter how the boxes themselves are configured or labeled.



For example, if there are 7 balls and 3 boxes, there would be four such ways to arrange them:




  1. O|O|OOOOO

  2. O|OO|OOOO

  3. O|OOO|OOO

  4. OO|OO|OOO


I have no ideas how to construct a formula for this










share|cite|improve this question









$endgroup$








  • 3




    $begingroup$
    What you are looking for is the number of partitions of $n$ into $k$ parts: whitman.edu/mathematics/cgt_online/book/section03.03.html. This is complicated to solve. I don't believe there is a nice formula for it, but there is a recurrence relation $p_k(n)=p_k(n-k)+p_{k-1}(n-1)$.
    $endgroup$
    – kccu
    Jan 26 at 4:22












  • $begingroup$
    @kccu I didn't recognize this as partitions, wow. But, didn't Ramanujan find an infinite series that converges to the solution of specific partitions? As far as I can remember, that series was very crazy and messy
    $endgroup$
    – KKZiomek
    Jan 26 at 4:28










  • $begingroup$
    I'm not familiar with that, but I wouldn't be surprised if Ramanujan had some sort of result about partitions.
    $endgroup$
    – kccu
    Jan 26 at 4:29










  • $begingroup$
    The generating function for partitions into $k$ parts goes back to Euler. Ramanujan did discover a considerable number of theorems about partitions and partition generating functions.
    $endgroup$
    – Peter Taylor
    Jan 28 at 10:58
















1












$begingroup$


Usually, when counting the number of ways in which $n$ balls can be put into $k$ boxes, two cases are considered:




  1. Boxes cannot be empty

  2. Boxes can be empty


Respectively, each of the listed cases has a formula:



$$C_1={n-1choose k-1}$$
$$C_2={n+k-1choose n}$$



This however doesn't suffice my needs. I want the boxes to be all not empty, and be countable, just like in the first case... But I want the boxes to be indistinguishable.



That is, as long as you have 4 balls in box 1, 2 balls in box 2, and 1 ball in box 3, it doesn't matter how the boxes themselves are configured or labeled.



For example, if there are 7 balls and 3 boxes, there would be four such ways to arrange them:




  1. O|O|OOOOO

  2. O|OO|OOOO

  3. O|OOO|OOO

  4. OO|OO|OOO


I have no ideas how to construct a formula for this










share|cite|improve this question









$endgroup$








  • 3




    $begingroup$
    What you are looking for is the number of partitions of $n$ into $k$ parts: whitman.edu/mathematics/cgt_online/book/section03.03.html. This is complicated to solve. I don't believe there is a nice formula for it, but there is a recurrence relation $p_k(n)=p_k(n-k)+p_{k-1}(n-1)$.
    $endgroup$
    – kccu
    Jan 26 at 4:22












  • $begingroup$
    @kccu I didn't recognize this as partitions, wow. But, didn't Ramanujan find an infinite series that converges to the solution of specific partitions? As far as I can remember, that series was very crazy and messy
    $endgroup$
    – KKZiomek
    Jan 26 at 4:28










  • $begingroup$
    I'm not familiar with that, but I wouldn't be surprised if Ramanujan had some sort of result about partitions.
    $endgroup$
    – kccu
    Jan 26 at 4:29










  • $begingroup$
    The generating function for partitions into $k$ parts goes back to Euler. Ramanujan did discover a considerable number of theorems about partitions and partition generating functions.
    $endgroup$
    – Peter Taylor
    Jan 28 at 10:58














1












1








1





$begingroup$


Usually, when counting the number of ways in which $n$ balls can be put into $k$ boxes, two cases are considered:




  1. Boxes cannot be empty

  2. Boxes can be empty


Respectively, each of the listed cases has a formula:



$$C_1={n-1choose k-1}$$
$$C_2={n+k-1choose n}$$



This however doesn't suffice my needs. I want the boxes to be all not empty, and be countable, just like in the first case... But I want the boxes to be indistinguishable.



That is, as long as you have 4 balls in box 1, 2 balls in box 2, and 1 ball in box 3, it doesn't matter how the boxes themselves are configured or labeled.



For example, if there are 7 balls and 3 boxes, there would be four such ways to arrange them:




  1. O|O|OOOOO

  2. O|OO|OOOO

  3. O|OOO|OOO

  4. OO|OO|OOO


I have no ideas how to construct a formula for this










share|cite|improve this question









$endgroup$




Usually, when counting the number of ways in which $n$ balls can be put into $k$ boxes, two cases are considered:




  1. Boxes cannot be empty

  2. Boxes can be empty


Respectively, each of the listed cases has a formula:



$$C_1={n-1choose k-1}$$
$$C_2={n+k-1choose n}$$



This however doesn't suffice my needs. I want the boxes to be all not empty, and be countable, just like in the first case... But I want the boxes to be indistinguishable.



That is, as long as you have 4 balls in box 1, 2 balls in box 2, and 1 ball in box 3, it doesn't matter how the boxes themselves are configured or labeled.



For example, if there are 7 balls and 3 boxes, there would be four such ways to arrange them:




  1. O|O|OOOOO

  2. O|OO|OOOO

  3. O|OOO|OOO

  4. OO|OO|OOO


I have no ideas how to construct a formula for this







probability combinatorics






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Jan 26 at 4:10









KKZiomekKKZiomek

2,2541641




2,2541641








  • 3




    $begingroup$
    What you are looking for is the number of partitions of $n$ into $k$ parts: whitman.edu/mathematics/cgt_online/book/section03.03.html. This is complicated to solve. I don't believe there is a nice formula for it, but there is a recurrence relation $p_k(n)=p_k(n-k)+p_{k-1}(n-1)$.
    $endgroup$
    – kccu
    Jan 26 at 4:22












  • $begingroup$
    @kccu I didn't recognize this as partitions, wow. But, didn't Ramanujan find an infinite series that converges to the solution of specific partitions? As far as I can remember, that series was very crazy and messy
    $endgroup$
    – KKZiomek
    Jan 26 at 4:28










  • $begingroup$
    I'm not familiar with that, but I wouldn't be surprised if Ramanujan had some sort of result about partitions.
    $endgroup$
    – kccu
    Jan 26 at 4:29










  • $begingroup$
    The generating function for partitions into $k$ parts goes back to Euler. Ramanujan did discover a considerable number of theorems about partitions and partition generating functions.
    $endgroup$
    – Peter Taylor
    Jan 28 at 10:58














  • 3




    $begingroup$
    What you are looking for is the number of partitions of $n$ into $k$ parts: whitman.edu/mathematics/cgt_online/book/section03.03.html. This is complicated to solve. I don't believe there is a nice formula for it, but there is a recurrence relation $p_k(n)=p_k(n-k)+p_{k-1}(n-1)$.
    $endgroup$
    – kccu
    Jan 26 at 4:22












  • $begingroup$
    @kccu I didn't recognize this as partitions, wow. But, didn't Ramanujan find an infinite series that converges to the solution of specific partitions? As far as I can remember, that series was very crazy and messy
    $endgroup$
    – KKZiomek
    Jan 26 at 4:28










  • $begingroup$
    I'm not familiar with that, but I wouldn't be surprised if Ramanujan had some sort of result about partitions.
    $endgroup$
    – kccu
    Jan 26 at 4:29










  • $begingroup$
    The generating function for partitions into $k$ parts goes back to Euler. Ramanujan did discover a considerable number of theorems about partitions and partition generating functions.
    $endgroup$
    – Peter Taylor
    Jan 28 at 10:58








3




3




$begingroup$
What you are looking for is the number of partitions of $n$ into $k$ parts: whitman.edu/mathematics/cgt_online/book/section03.03.html. This is complicated to solve. I don't believe there is a nice formula for it, but there is a recurrence relation $p_k(n)=p_k(n-k)+p_{k-1}(n-1)$.
$endgroup$
– kccu
Jan 26 at 4:22






$begingroup$
What you are looking for is the number of partitions of $n$ into $k$ parts: whitman.edu/mathematics/cgt_online/book/section03.03.html. This is complicated to solve. I don't believe there is a nice formula for it, but there is a recurrence relation $p_k(n)=p_k(n-k)+p_{k-1}(n-1)$.
$endgroup$
– kccu
Jan 26 at 4:22














$begingroup$
@kccu I didn't recognize this as partitions, wow. But, didn't Ramanujan find an infinite series that converges to the solution of specific partitions? As far as I can remember, that series was very crazy and messy
$endgroup$
– KKZiomek
Jan 26 at 4:28




$begingroup$
@kccu I didn't recognize this as partitions, wow. But, didn't Ramanujan find an infinite series that converges to the solution of specific partitions? As far as I can remember, that series was very crazy and messy
$endgroup$
– KKZiomek
Jan 26 at 4:28












$begingroup$
I'm not familiar with that, but I wouldn't be surprised if Ramanujan had some sort of result about partitions.
$endgroup$
– kccu
Jan 26 at 4:29




$begingroup$
I'm not familiar with that, but I wouldn't be surprised if Ramanujan had some sort of result about partitions.
$endgroup$
– kccu
Jan 26 at 4:29












$begingroup$
The generating function for partitions into $k$ parts goes back to Euler. Ramanujan did discover a considerable number of theorems about partitions and partition generating functions.
$endgroup$
– Peter Taylor
Jan 28 at 10:58




$begingroup$
The generating function for partitions into $k$ parts goes back to Euler. Ramanujan did discover a considerable number of theorems about partitions and partition generating functions.
$endgroup$
– Peter Taylor
Jan 28 at 10:58










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