# Problem with sigma notation

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

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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.

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]

Feldoh
Do you know what a factoral is?

Four
Do you know what a factoral is?

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