positive integer factorial means multiplying from 1 times 2 times 3 times 4 all the way up to the required number.

for example, if the required number is 4, then the factorial formula is 1×2×3×4, and the resulting product is 24, which is the factorial of 4. for example, the required number is 6, then the factorial formula is 1×2×3×…×6, and the resulting product is 720, and 720 is the factorial of 6. for example, the required number is n, then the factorial formula is 1×2×3×…×n. assume that the obtained product is x, and x is the factorial of n.

the factorial representation of any natural number n greater than 1:

n!=1×2×3×…×n or n!=n×(n-1)!