This function calculates the double factorial of the specified number.
The argument can be any non-negative numeric value.
The number argument must be a non-negative number. If you provide a number that is not an integer for the number argument, the decimal portion of the number is ignored. The double factorial is calculated as follows for even numbers:
n!! = n(n-2)(n-4) ... (4)(2)
The double factorial is calculated as follows for odd numbers:
n!! = n(n-2)(n-4) ... (3)(1)
Accepts numeric data. Returns numeric data.
FACTDOUBLE(6) gives the result 48