The factorial of n is denoted by n! and calculated by the product of integer numbers from 1 to n.
For n>0,
n! = 1×2×3×4×...×n
For n=0,
0! = 1
Examples:
1! = 1
2! = 1×2 = 2
3! = 1×2×3 = 6
4! = 1×2×3×4 = 24
5! = 1×2×3×4×5 = 120
n! = n×(n-1)!
Example:
5! = 5×(5-1)! = 5×4! = 5×24 = 120
Example:
5! ≈ √2π5⋅55⋅e-5 = 118.019
Number n |
Factorial n! |
---|---|
0 | 1 |
1 | 1 |
2 | 2 |
3 | 6 |
4 | 24 |
5 | 120 |
6 | 720 |
7 | 5040 |
8 | 40320 |
9 | 362880 |
10 | 3628800 |
11 | 3.991680x107 |
12 | 4.790016x108 |
13 | 6.227021x109 |
14 | 8.717829x1010 |
15 | 1.307674x1012 |
16 | 2.092279x1013 |
17 | 3.556874x1014 |
18 | 6.402374x1015 |
19 | 1.216451x1017 |
20 | 2.432902x1018 |
double factorial(unsigned int n)
{
double fact=1.0;
if( n > 1 )
for(unsigned int k=2; k<=n; k++)
fact = fact*k;
return fact;
}