# Problem with sigma notation

1. May 3, 2007

### kevinater2007

must express this series using sigma notation

5+5+5/2+5/6+5/24+...

i would be extremely grateful for some help

I know that you use the infinite symbol and it goes above sigma and then n=1 below it.
i also have used the arithmetic series equations and geometric equations on several other problems but i don't know where to start when the equation doesn't consist of one of these two and when the ratio isn't a constant additive, divisor, subtractor, or multiplicative

Last edited: May 3, 2007
2. May 3, 2007

### neutrino

Look at the numbers in the denominators. Do they remind you of something: 1,1,2,6,24,...? (No, it's not the Fibonacci series!) Pay attention to how one number is related to the subsequent one.

3. May 4, 2007

### Four

As neutrino mentioned the denominator is interesting. Also just a note 0!=1 = 1!. This is the usuall definition.

[This hint I think really gives the answer away]

4. May 5, 2007

### Feldoh

Do you know what a factoral is?

5. May 6, 2007

### Four

Who are you refering too? I was reading this and made me wonder maby I was thinking wrong? I know whats a factorial and in my classes usually 0! is defined to be 1. Which was shown using the binomial theorum as I remember.