1014 C语言程序设计教程（第三版）课后习题6.4

 1 #include "stdio.h"
 2 
 3 int main(int argc, char const *argv[])
 4 {
 5     
 6     int i, n;
 7     long long int Sn = 0, factor = 1;
 8     scanf("%d", &n);
 9 
10     for(i = 1; i <= n; i++)
11     {
12         Sn += factor;
13         factor = factor * (i + 1);
14     }
15 
16     printf("%lld\n", Sn);
17     return 0;
18 }