Factorial factor is an operation symbol invented by Keyston Kramp (1760 ~1826) in 1808, and it is a mathematical term.
The factorial of a positive integer is the product of all positive integers less than or equal to this number, and the factorial of 0 is 1. The factorial writing of natural number n! . In 1808, Keyston Kaman introduced this symbol.
Extended data Usually, the factorial we are talking about is defined in the range of natural numbers (most scientific calculators can only calculate the factorial of 0 ~ 69), and decimal scientific calculators have no factorial function, such as 0.5! ,0.65! ,0.777! It's all wrong But sometimes we define the Gamma function as the factorial of non-integers, because when x is a positive integer n, the value of the Gamma function is the factorial of n- 1
References:
Baidu encyclopedia-factorial