# Mathematics-Factorial

Factorial of a non-negative integer, n is denoted as n!. And it is calculated using product of all positive integers less than or equal to n.

Eg ) 5! = 5 * 4 * 3 * 2 * 1 = 120

The notation n! is introduced by Christian Kramb.

Factorial function defined normally by n! =

or it is denoted recursively by n! = 1 if n = 0

(n - 1)! * n if n > 0

Factorial function is denoted by using a symbol ' ! ' . It means to multiply a series of descending natural numbers.

4! = 4 * 3 * 2 * 1 = 24

Main usage of factorial is in permutation & combination**Half Factorial :: **

Factorial of a half ( 1/2 ) is half of the square root of ( pi ) ∏.

eg ) ( 1/2 ) ! = ( 1/2 )√∏

To conclude factorial of a any number is that number times the factorial of 1 less than that number.