Formulas and functions > Functions from A to Z > FACTDOUBLE (double factorial)

Syntax:

FACTDOUBLE(Number)

Description:

This returns the double factorial of a number.

The double factorial is calculated as follows:

If Number is even, its double factorial is 2*4*6*...*Number.

If Number is odd, its double factorial is 1*3*5*...*Number.

Number must be ≥ 0. Decimal places are automatically truncated.

Example:

FACTDOUBLE(10) corresponds to 2*4*6*8*10, which equals 3840.

FACTDOUBLE(11) corresponds to 1*3*5*7*9*11, which equals 10395.