求级数公式，对应的代码

求大佬写出这个公式对应的代码，不要用pow函数

供参考：

#include <stdio.h>
int main()
{
    double sum = 1, x, X = 1, tmp;
    int n, temp, sign = -1, count = 1;
    scanf("%d %lf", &n, &x);
    while (count <= n)
    {
        X *= x * x;
        if (count == 1) {
            tmp = 2.0;
            temp = 2;
        }
        else {
            tmp *= (temp + 1)*(temp + 2);
            temp += 2;
        }
        sum += sign * X / tmp;
        sign = -sign;
        count++;
    }
    printf("S=%f", sum);
    return 0;
}