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) returns 384 (=8 • 6 • 4 • 2).