How to express multiplication of n numbers?

hello, everyone. Given n numbers a_i (i=1...n), how to exactly express multiplication of n numbers?
which one of the following expressions is best? Or you have any other suggestions?
"multiplication of a_is"
"multiplication of a_i"
"series multiplication of a_is"
"series multiplication of a_i"

This is not a kind of writing I know about! Ha ha, I don't even know how to research it! What kind of math class are you taking?

I don't quite exactly understand your notation or the way you asked that but I would say

"multiplication of ai"

One usually says "the product of a_i s"