 # 9!!

## Enter Multifactorial

Calculate the multifactorial 9!!
We have 2 exclamation symbols (!)
Start at 9
Iterate backwards in steps of 2
Stop when we hit 1 or below

## Term 2

Subtract -1 x 2 = -2 to get n(n - -2)
(n - -2) → 9 - -2 = 7
Our factorial term is:
9(7)

## Term 3

Subtract -1 x 2 = -2 to get n(n - -2)(n - -2)
(n - -2) → 9 - -2 = 5
Our factorial term is:
9(7)(5)

## Term 4

Subtract -1 x 2 = -2 to get n(n - -2)(n - -2)(n - -2)
(n - -2) → 9 - -2 = 3
Our factorial term is:
9(7)(5)(3)

## Term 5

Subtract -1 x 2 = -2 to get n(n - -2)(n - -2)(n - -2)(n - -2)
(n - -2) → 9 - -2 = 1
Our factorial term is:
9(7)(5)(3)(1)

9!! = n(n - -2)(n - -2)(n - -2)(n - -2)...
9!! = 9(7)(5)(3)(1)  9!! = 945

### How does the Multifactorials Calculator work?

Free Multifactorials Calculator - Calculates the multifactorial n!(m)
This calculator has 1 input.

### What 1 formula is used for the Multifactorials Calculator?

n!(m) = (n - m) * (n - m - m) * ... * 1

For more math formulas, check out our Formula Dossier

### What 3 concepts are covered in the Multifactorials Calculator?

factorial
The product of an integer and all the integers below it
multifactorial
generalisation of a factorial in which each element to be multiplied differs from the next by an integer
permutation
a way in which a set or number of things can be ordered or arranged.
nPr = n!/(n - r)!