Microsoft® Excel® 2010 Formulas & Functions Inside Out

FACTDOUBLE()

Syntax. FACTDOUBLE(number)

Definition. This function returns the double factorial of a number.

Argument

• number (required) The value for which to return the double factorial. If number isn’t an integer, the decimal places are truncated.

Background. The factorial n! of number n is defined as follows:

n! = n(n – 1)(n – 2)...(3)(2)(1)

The FACTDOUBLE() function for even numbers is defined as follows:

n!! = n(n – 2)(n – 4)...(4)(2)

and for odd numbers:

n!! = n(n – 2)(n – 4)...(3)(1)

The FACTDOUBLE() function uses numeric values. If number isn’t a numeric value, the FACTDOUBLE() function returns the #VALUE! error. If number is negative, FACTDOUBLE() returns the #NUM! error value.

More examples:

• =FACTDOUBLE(5) returns 15 (=5 • 3 • 1).

• =FACTDOUBLE(8)