 This can be seen by interpreting the denominator to be the arithmetic mean of the product of numbers "n" times but each time omitting the "j"-th term.That is, for the first term, we multiply all "n" numbers except the first; for the second, we multiply all "n" numbers except the second; and so on.The numerator, excluding the "n", which goes with the arithmetic mean, is the geometric mean to the power "n".