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## #1 2012-10-28 20:51:18

Harold
Guest

### Multifactorial

How do you define multifactorial?I know what it is,but how do you define it?I know how to define factorial.

## #2 2012-10-28 21:12:14

anonimnystefy
Real Member
From: Harlan's World
Registered: 2011-05-23
Posts: 16,018

### Re: Multifactorial

Here lies the reader who will never open this book. He is forever dead.
Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment
The knowledge of some things as a function of age is a delta function.

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## #3 2012-10-28 23:00:35

Harold
Guest

### Re: Multifactorial

Can't this be another definition-

## #4 2012-10-29 00:26:57

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,190

### Re: Multifactorial

Hi Harold;

Did you try one? Say for k = 3.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #5 2012-10-29 00:48:16

Harold
Guest

### Re: Multifactorial

Well,if I try n=11,k=3,then11!!!=11*8*5*2(as 11 mod 3=2) =880,is it correct?

## #6 2012-10-29 01:09:14

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,190

### Re: Multifactorial

Hi;

That is correct. Now what do you get for 20!!!! ?

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #7 2012-10-29 01:47:18

Harold
Guest

### Re: Multifactorial

Well,thank you,I love solving problems,now,20!!!!,so n=20 and k=4
20!!!!=20(20-4)(20-4*2)(20-4*3)...(4) [as 20 mod 4=0]=20*16*12*8*4=122880.

## #8 2012-10-29 01:57:27

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,190

### Re: Multifactorial

Hi;

That is correct. Your formula looks fine to me. Although there is a better one on that page that anonimnystefy sent you.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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## #9 2012-10-29 02:40:30

Harold
Guest

### Re: Multifactorial

But,I am confused,if I do 11!!! by the method in wikipedia,I get 11!!!=11(8!!!)=11(8(5!!!))=11(8(5(2!!!)))=11(8(5(1))) [as 0<2<3] =440
and by my method,I get 11!!!=11(11-3)(11-2*3)...(2)=11*8*5*2=880
which is correct ??

## #10 2012-10-29 02:44:34

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 107,190

### Re: Multifactorial

2!!! = 2 not 1.

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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