Number of partitions of 2N into N parts

In summary, the number of partitions of an even number 2N into N parts appears to be equal to the number of partitions of N. This fact is known and can be proven using a bijective proof involving Ferrer's diagrams. Additionally, this idea can be extended to show that the number of partitions of a positive integer m into j parts is equal to the number of partitions of m-j when m is greater than j and j is greater than or equal to half of m.
  • #1
FaustoMorales
24
0
The number of partitions of an even number 2N into N parts appears to be equal to the number of partitions of N.

Is this known? If so: Can anyone provide a reference of the corresponding proof? Thanks in advance for any information on this.
 
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  • #2
The number of partitions of any integer m into j parts equals the number of partitions of m with largest part j (easy bijective proof using Ferrer's diagrams). Thus the number of partitions of 2n into n parts equals the number of partitions of 2n with largest part n. The bijection between partitions of 2n with largest part n and partitions of n is straightforward.
 
  • #3
That takes care of it. Thanks!
 
  • #4
JCVD said:
The number of partitions of any integer m into j parts equals the number of partitions of m with largest part j (easy bijective proof using Ferrer's diagrams). Thus the number of partitions of 2n into n parts equals the number of partitions of 2n with largest part n. The bijection between partitions of 2n with largest part n and partitions of n is straightforward.

This clever idea can be used to prove something more general: Given positive integers m and j, with m > j >= m/2, the number of partitions of m into j parts is the number of partitions of m-j.
 
  • #5


This phenomenon is known as the "Ferrers graph method" and has been studied extensively in combinatorics. It has been proven that the number of partitions of 2N into N parts is equal to the number of partitions of N. This proof can be found in various mathematical journals and textbooks, such as "Introduction to Combinatorics" by Richard A. Brualdi and "Partition Theory" by George E. Andrews. Additionally, there are many online resources available that discuss and prove this result.
 

1. What is the formula for calculating the number of partitions of 2N into N parts?

The formula for calculating the number of partitions of 2N into N parts is given by the Bell number, which can be expressed as B(2N) = (2N)! / (2^N * N!)

2. Can you provide an example of a partition of 2N into N parts?

Yes, for N = 3, a possible partition of 2N = 6 into N = 3 parts would be {1, 1, 4}, {1, 2, 3}, {2, 2, 2}.

3. How does the number of partitions of 2N into N parts increase as N increases?

As N increases, the number of partitions of 2N into N parts also increases. This can be seen by looking at the Bell numbers, which grow rapidly as N increases.

4. What is the significance of the number of partitions of 2N into N parts in mathematics?

The number of partitions of 2N into N parts has many applications in combinatorics, number theory, and other areas of mathematics. It is also related to the Stirling numbers of the second kind, which have important uses in the study of permutations and combinations.

5. Can the number of partitions of 2N into N parts be used in real-world problems?

Yes, the number of partitions of 2N into N parts has practical applications in fields such as computer science, physics, and economics. For example, it can be used in analyzing the number of ways to distribute objects among a given number of containers or to model the distribution of energy among particles in a system.

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