[Marcotte]

Sorry, should have said expected outcome. I'm looking for the value of the roll. There is no betting involved.

If I roll one die (keeping it all six-sided for simplicity) the expected outcome is 3.5. If I roll two then I have the following possible outcomes
prob. outcome
1/36 1
3/36 2
5/36 3
7/36 4
9/36 5
11/36 6

for an expected outcome of 4.47

What I'm looking for is a formula to calculate that number given X, the number of dice used, and Y, the number of sides each die has. Hopefully that makes more sense.