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**JonathanS****Member**- Registered: 2011-10-14
- Posts: 2

Hello, I visited mathsisfun.com/combinatorics/combinations-permutations-calculator.html and would like to get the source code for the combination where order matters and no repeats.

The one that is n!/(n-r)!

I would be using it for a program I am making that outputs all possible tetrahedral molecules.

Thanks!

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 92,926

Hi JonathanS;

There is some confusion here.

like to get the source code for the combination where order matters and no repeats.

When order matters it is called a permutation.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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**JonathanS****Member**- Registered: 2011-10-14
- Posts: 2

ah k, got to google some algorithms for permutations, thanks!

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 92,926

Hi JonathanS;

You should be able to find many of them.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

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