GEOMEAN function
Description
Geometric mean function. GEOMEAN(range) computes the geometric mean of the contents of the cells in the specified range.
The geometric mean is calculated as follows:
$$\left ( \prod_{i=1}^n{x_i} \right ) ^\tfrac1n = \sqrt[n]{x_1 x_2 \cdots x_n} = \exp\left[\frac1n\sum_{i=1}^n\ln x_i\right] $$ The geometric mean is undefined for a data set that contains zero or negative values.