# Math Help - Evaluate this summation (computer help needed!)

1. ## Evaluate this summation (computer help needed!)

Hello

Where can I find a good online tool to evaluate this expression?

This refers to the expected value of a random variable, related to a card game (Yu-Gi-Oh, if you need to know!).

Wolframalpha isn't able to compute it (the expression exceeds the size of the form where you write your question...)

Thanks!

2. Wolfram|Alpha&mdash;Computational Knowledge Engine

Or if you are a student, there should be some computers on campus with Mathematica Pro, Maple, or MatLab.

3. Originally Posted by Erik1089
Wolframalpha isn't able to compute it
...

4. I used to judge Yu-Gi-Oh events when Upper Deck was still around.

I punched your expression into Mathematica, but there is some trouble with one part of the summation. The term $(n - 1 - i - j - k - l)$ is sometimes negative, making it impossible to evaluate the factorial. Can you correct this?

5. dwsmith: Yeah, I'm a student in a campus, but I don't know how to use any of those programs, so I figured an online tool would be the best!

roninpro: The negative factorials are supposed to be interpreted as zero. Well, not actually the factorials, but the binomials with negative bottom number, which happen together with the negative factorials and are usually zero by convention. That's why I wrote things like
$\binom{a}{b} b!$
$\dfrac{a!}{(a-b)!}$ ,
because of those cases where the bottom number is negative.

The only way to correct this would be to write each one of the 34 summands individually... But thanks anyway!

EDIT: Well, not quite 34 summands... 34 X 81 summands!

6. I could simply define a piecewise function in Mathematica to take that convention into consideration. I will take a look at it a bit later, when I have the time.