Skip to main content

FACTDOUBLE

The FACTDOUBLE function returns the double factorial of a number.

A double factorial is the product of all integers of the same sign that are less than or equal to a given number, with an increment of 2.

Syntax​

FACTDOUBLE(value)

ArgumentDescriptionPermitted values
valueNumber or reference to a number for which the double factorial is calculated0, 1, 2, 3, ... (non-negative integers) or a reference to a cell containing a number

Examples of use​

Calculating the double factorial of the number 5

=FACTDOUBLE(5)

Result: 15, since 5!!=5×3×1.

Calculating the double factorial of the number 6

=FACTDOUBLE(6)

Result: 48, since 6!!=6×4×2.

Notes​

  • If the argument is not an integer, it is truncated to an integer.
  • The double factorial for non-negative integers is defined as:
    • n!! = n × (n−2) × (n−4) × ... × 2 — for even numbers.
    • n!! = n × (n−2) × (n−4) × ... × 1 — for odd numbers.