FACTDOUBLE
Returns the double factorial of a number.
Syntax:
FACTDOUBLE(number)
returns number!!, the double factorial of number, where number is an integer greater than or equal to zero.
For even numbers FACTDOUBLE(number) returns:
2*4*6*8* ... *number
For odd numbers FACTDOUBLE(number) returns:
1*3*5*7* ... *number
FACTDOUBLE(0) returns 1 by definition.
Example:
FACTDOUBLE(5)
returns 15.
FACTDOUBLE(6)
returns 48.
FACTDOUBLE(0)
returns 1.
