The Excel FACTDOUBLE Function

Double Factorial

The Double Factorial of a number, N, is given by the following:

If N is even:

N * (N-2) * (N-4) * ... * 4 * 2

If N is odd:

N * (N-2) * (N-4) * ... * 3 * 1

For further details, see the Wikipedia Factorial page

Related Function:
FACT Function

Function Description

The Excel Factdouble function returns the double factorial of a supplied number.

The syntax of the function is:

FACTDOUBLE( number )

where the number argument is the positive integer that you want to calculate the double factorial of.

Factdouble Function Examples

Cells A1-A3 of the following spreadsheet shows examples of the Excel Factdouble function, used to calculate the double factorial of the integers 5, 8 and 13.

Formulas:
AB
1=FACTDOUBLE( 5 )= 5 x 3 x 1
2=FACTDOUBLE( 8 )= 8 x 6 x 4 x 2
3=FACTDOUBLE( 13 )= 13 x 11 x 9 x 7 x 5 x 3 x 1
Results:
AB
115= 5 x 3 x 1
2384= 8 x 6 x 4 x 2
3135135= 13 x 11 x 9 x 7 x 5 x 3 x 1

Further examples of the Excel Factdouble function are provided on the Microsoft Office website.

Excel Factdouble Function Errors

If you get an error from the Excel Factdouble function this is likely to be one of the following:

Common Errors
 #NUM! - Occurs if the supplied number is < 0. #VALUE! - Occurs if the supplied number is non-numeric.