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Combinatorics

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3 items for Combinatorics
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This post has a impact factor of 35 and 977 pageviews

Sum of subsets with k elements having a total sum of r

This question is a mirror of the question Sum of subsets which I found interesting. The problem is like this:

Let , how many subsets with k elements that are having the sum of value r?

For instance, if n = 6, k = 3, r = 10:

The following sets: ...

sciencolic 19 Aug 10 |1 answer
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30
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This post has a impact factor of 30 and 1160 pageviews

Repeated sum and partial difference equation

This paper is inspired by this post. It asked how to count the number of solutions of the equation with non-negative integral solution:

x_1 + ... + x_k = n

without using the standard method of line and dot counting. I transform the problem into a partial difference equation, ...

ross_tang 08 Aug 10
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This post has a impact factor of 12 and 912 pageviews

A procedure to list all derangements of a multiset

This article provides and describes a Python function to list all the derangements of a multiset.

ross_tang 19 May 10
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ross_tang

Degree in Physics and Mathematics, Master in Physics
香港

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sciencolic

I love Physics, Mathematics and Science.
Japan