The Excel FACTDOUBLE function returns the double factorial of a number. A double factorial is symbolized by two exclamation marks (!!).
Get double factorial of a number
number - A number greater than or equal to -1.
The FACTDOUBLE function returns the double factorial of a number. A double factorial is calculated differently for even and odd numbers. For an even number, n, it's the product of all even integers less than or equal to n and greater than or equal to 2. For an odd number, the double factorial is the product of all odd integers less than or equal to n and greater than or equal to 1. The double factorial for both zero and -1 are defined as 1. For numbers less than -1, a double factorial is not defined.
The Excel FACT function returns the factorial of a given number. For example, =FACT(3) returns 6, equivalent to 3 x 2 x 1.
Excel Formula Training
Formulas are the key to getting things done in Excel. In this accelerated training, you'll learn how to use formulas to manipulate text, work with dates and times, lookup values with VLOOKUP and INDEX & MATCH, count and sum with criteria, dynamically rank values, and create dynamic ranges. You'll also learn how to troubleshoot, trace errors, and fix problems. Instant access. See details here.