Double factorial

product of all the integers from 1 up to the integral input of the function that have the same parity as this input

Double factorial is a method of calculating how many times a number is repeated in a geometric equation. This way, we can calculate the number of times a product is used in its life-time.

The double factorial of n is written as .[1] When n is a positive odd integer, is defined as . When n is an positive even integer, is defined as . By definition, .[2][3]

Related pagesEdit


  1. "List of Probability and Statistics Symbols". Math Vault. 2020-04-26. Retrieved 2020-09-10.
  2. Weisstein, Eric W. "Double Factorial". Retrieved 2020-09-10.
  3. "Double Factorials and Multifactorials | Brilliant Math & Science Wiki". Retrieved 2020-09-10.