质因子个数

// 质因子个数
int num[MAXN];

inline void init()
{
    num[1] = 0;
    for (int i = 2; i < MAXN; ++i)
    {
        if (!num[i])
        {
            num[i] = 1;
            for (int j = i + i; j < MAXN; j += i)
            {
                int temp = j;
                while (temp % i == 0)
                {
                    ++num[j];
                    temp /= i;
                }
            }
        }
    }
}