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### Factorial Notation

```
Date: 9/8/96 at 14:17:42
From: Anonymous
Subject: Determining Infinite Series

I am supposed to tell if series (1+1/1!+1/2!+1/3! ...) is infinite. I
can't even start it because I don't even know what the "!" means...
can you help me?
```

```
Date: 9/12/96 at 10:22:16
From: Doctor Ken
Subject: Re: Determining Infinite Series

Hello!

I'll tell you what the ! means, and then you see whether you can
figure it out from there, okay?  There's a joke in math that the ! is
someone's attempt to make math LOOK interesting.  You know, it's not
just 7, it's 7!  Anyway, it actually does have a precise meaning, and
it's pretty neat too.

7! = 7*6*5*4*3*2*1.  Also, 10! = 10*9*8*7*6*5*4*3*2*1.

The symbol ! is called "factorial."  So 7! is seven factorial.

Now what do you think about your problem?

-Doctor Ken,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
```
Associated Topics:
High School Definitions

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