Returns the double factorial of a number.
Syntax
FACTDOUBLE(number)
Number is the value for which to return the double factorial. If number is not an integer, it is truncated.
Remarks
 If number is nonnumeric, FACTDOUBLE returns the #VALUE! error value.
 If number is negative, FACTDOUBLE returns the #NUM! error value.
 If number is even:
Example
The example may be easier to understand if you copy it to a blank worksheet.
How to copy an example
 Create a blank workbook or worksheet.
 Select the example in the Help topic.
Note Do not select the row or column headers.
Selecting an example from Help
 Press CTRL+C.
 In the worksheet, select cell A1, and press CTRL+V.
 To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

A 
B 
Formula 
Description (Result) 
=FACTDOUBLE(6) 
Double factorial of 6 (48) 
=FACTDOUBLE(7) 
Double factorial of 7 (105) 
