Questions tagged [integer-partitions]

Use this tag for questions related to ways of writing a positive integer as a sum of positive integers.

In number theory and combinatorics, a partition of a positive integer $n$ is a way of writing $n$ as a sum of positive integers. Two sums that differ only in the order of their summands (also called parts) are considered the same partition. For example, all of the partitions of $4$ are $1 + 1 + 1 + 1$, $2 + 1 + 1$, $2 + 2$, $3 + 1$, or $4$.

The number of partitions of $n$ is given by the partition function $p(n)$. For the example above, $p(4) = 5$.

Partitions can be visualized graphically with Ferrers diagrams.

Partitions have applications in symmetric polynomials, the symmetric group, and group representations.

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Why 3 power to n will always get a sum of digit equal to 9?

Why the sum of digits of $3^n$ or $(x·3)^n$ for $n \geq 2 \subset Z$, $x \geq 1 \subset Z$ always equal to 9? For some sample cases: $3^2 = 9$ $3^3 = 27 = 2 + 7 = 9$ $3^4 = 81 = 8 + 1 = 9$ $3^5 = 243 = 2 + 4 + 3 = 9$ $(33·3)^5 = 99^5 = 9509900499 =…
yzh1206
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Write a number as a sum of odd number of integers

Suppose that I have 2 positive integers $N$ and $K$ $(K \ge 3)$, I want to write $N = 1*x + 2*y + K*z$. All $x, y,z$ are non-negative integers. $z$ should be $\lfloor\frac{N}{K}\rfloor$ or $\lfloor\frac{N}{K}\rfloor - 1$. Are there any ways to…
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Is my answer correct? Partitioning numbers

How many ways are there to write the number 7 with the summands: 1, 2, and 3? For example, there are 7 ways to write the number 4: {1 + 1 + 1 + 1} x 1 {2 + 1 + 1} x 3 {3 + 1} x 2 {2 + 2} x 1 I got the answer 44 by doing so: {1 + 1 + 1 + 1 + 1 + 1…
Godlixe
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limit of ratio of partition function

Does the following limit exists? $$\lim_{n \rightarrow \infty} \frac{p(n)}{p(n-5)}$$ where $p(n)$ denote the partition function. If this limit exists, is it equal to 1? Kindly share your thoughts. Thank you.
GA316
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How to calculate the partitions of a concrete number?

This might be a super stupid question, but my math courses are long gone and I am stuck completely solving some math puzzles for fun. Just as a hobby, no homework involved. I want to calculate the number of ways N coins can be partitioned. I have…
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Interesting property of partitions of $n$

Let $n$ be a positive integer. Show that the number of partitions of $n$, having one part more than $\frac n2$, is equal to the number of partitions of $n$ having more than $\frac n2$ parts. The difficulty is in the fact that, a partition is not…
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On an example in Macdonald's Symmetric Functions and Hall Polynomials on Paritions and their Frobenius Notation

I am following Macdonald's Symmetric Functions and Hall Polynomials, and in his example-section. He stated the following without any proof, and I'm trying to understand how he reached the expression. Any assistance will be appreciated. A partition…
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Generating function for certain partition functions.

what is the generating function of partitions of n into positive integers where the integers come in two kinds and the second kind has weight 23 times the weight of the first kind. Does the coefficients occurring here are well known or is it…
GA316
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Space partitioning to contain same amount of points

Looking for an algorithm can partition space so, that each partition contains fix count of point i.e. 20 points. Which algorithm could solve problem?
János
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Partition Proof Using One-to-One Correspondences

Let $g(n,k)$ be the number of partitions of $n$ into exactly $k$ parts, in which no part is a $1$. Show that $$g(n,k) = g(n-2,k-1) + g(n-k,k).$$ I know that the solution involves a one-to-one correspondence. I tried listing a few examples, but I…
user359548
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Problem on partioning

On reading the book 'Aha! Solutions' by Martin Erickson I came to know that the number of partitions of $n$ ($n \in \mathbb{N}$) into three parts is $\left\{ {\frac{{{n^2}}}{{12}}} \right\}$ where $\left\{ {} \right\}$ denotes the nearest-integer…
Perth
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What is a Fixed Partition?

I have two partition, P= {$x_0,x_1,...,x_n$} and Q= {$y_0, y_1,...,y_n$}. P is a general partition of the interval of [a,b] and Q is a fixed partition of [a,b]. What does it mean for Q to be fixed? Does the number of points, n, in Q have to remain…
Tim
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Recurrence partition basic

I have some questions regarding (recurrence relation) for partitions, actually I do not know what is the exact term called (it was stated as partitions only in my guide book and upon doing some searches, it seems that the formula is somewhat…
dissidia
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Is $\mathbb R/R$ a partition of $\mathbb R$ given by some equivalence relation $R$?

Let $aRb $ iff $b - a$ is an integer. $5 - 0$ is an integer, so $5 \in [0].$ In fact, $[0] = \mathbb Z$. Does it mean $\mathbb Z \in \mathbb R/R$? $5.14159265359 - \pi$ is an integer, so $5.14159265359 \in [\pi]$ and $[\pi] \in \mathbb R/R$? Is…
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Bijective Proof - partitions

what is a bijective proof of #93 in the link provided http://math.mit.edu/~rstan/bij.pdf: The number of partitions of $n$ with $k$ parts equals the number of partitions of $n + \binom{k}{2}$ with $k$ distinct parts
John
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