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.

Which is n! =1× 2× 3× ...× n. The factor can also be defined recursively: 0! = 1，n！ =(n- 1)！ ×n .

The formula of factorial:

n！ =1× 2× 3× ...× n. The factor can also be defined recursively: 0! = 1，n！ =(n- 1)！ ×n .

For example, finding the value of 1x2x4 ... xn can be expressed by factorial:

n！ = 1× 2× 3× (n- 1) n or n! =(n- 1)！ ×n

With "m! ! "Express delivery.

When m is a natural number, it means the product of all positive integers not exceeding m and having the same parity with m.

Factorial factor refers to the required number obtained by multiplying 1 by 2 times 3 times 4. For example, if the required number is 4, the factorial formula is 1×2×3×4, and the product is 24, that is, the factorial of 4. ? For example, if the required number is 6, the factorial formula is 1× 2× 3×…× 6, and the product is 720, which is the factorial of 6.

For example, if the required number is n, the factorial formula is 1× 2× 3× …× n, and the product obtained is x, that is, the factorial of n. The factorial of any natural number greater than 1 means:? n！ = 1×2×3×……×n？ Or? n！ =n×(n- 1)！ ? ? 5! =5*4*3*2* 1= 120。