# FACTDOUBLE

## Content

This function calculates the double factorial of the specified number.

## Syntax

`FACTDOUBLE(number)`

## Arguments

[Required] The value for which to return the double factorial. If number is not an integer, it is truncated.

## Remarks

The *number* argument must be a non-negative number. If you provide a number that is not an integer for the *number* argument, the decimal portion of the number is ignored.
The double factorial is calculated as follows for even numbers:
`n!! = n(n-2)(n-4) ... (4)(2)`
The double factorial is calculated as follows for odd numbers:
`n!! = n(n-2)(n-4) ... (3)(1)`

## Examples

`FACTDOUBLE(E3)`
`FACTDOUBLE(R3C5)`
`FACTDOUBLE(6)` gives the result 48