求级数的和

#include 
double fun(double x, int n)
{
    double s = 1.0, y = x;
    int i;
    long k = 1;

    for (i = 1; i <= n; i++) {
        k = k * i;
        s += y / k;
        y *= x;
    }
    return s;
}
int main()
{
    printf("%f\n", fun(0.3, 10));
    return 0;
}