Number of elements in a summation set?

I was wondering if the attachment illustrating the development of the formula:

[S!/{(S-Z1-Z2-Z3...!)*(Z1!)*(Z2!)*(Z3!)...}]

is correct, or did I make a mistake somewhere?

-Lou

first off, the equation itself is right
(is essentially the same as picking, from the S objects, separate sets of Z1, Z2, Z3, ....S-Z1-Z2-Z3-....) - note that the last set is all elements which will be raised to the power of zero :)


And splitting it up like that looks perfectly fine...It's just like saying 'Pick Z1 objects from S, then Z2 from (S-Z1), then...'

So yeah, looks all fine to me :D
Certainly makes sense, if that's what ur asking.

Then only thing you might have to say is that none of the Ys can be zero...cos then it may as well not be there

Great!
Thanks for checking.

-Lou