欧拉函数

根据题目意思，需要用到欧拉函数， 接下来枚举就行

C++ 代码

#include <iostream>
#define endl '\n'
using namespace std;
const int N = 1001;
int primes[N], cnt;
int phi[N], a[N], res[N];
bool st[N];
inline void get(int x)
{
    phi[1] = 1;
    for (int i = 2; i <= x; i ++ )
    {
        if (!st[i])
        {
            primes[cnt ++] = i;
            phi[i] = i - 1;
        }
        for (int j = 0; primes[j] * i <= x; j ++ )
        {
            st[primes[j] * i] = true;
            if (i % primes[j] == 0)
            {
                phi[primes[j] * i] = phi[i] * primes[j];
                break;
            }
            phi[primes[j] * i] = phi[i] * phi[primes[j]];
        }
    }
}
int main()
{
    cin.tie(nullptr) -> sync_with_stdio(0);
    int t = 1, maxv = 0;
    cin >> t;
    for (int i = 1; i <= t; i ++ )
    {
        cin >> a[i];
        if (maxv < a[i]) maxv = a[i];
    }
    get(maxv);
    res[0] = 1;
    for (int i = 1; i <= maxv; i ++ ) res[i] = res[i - 1] + (phi[i] << 1);
    for (int i = 1; i <= t; i ++ )
    cout << i << " " << a[i] << " " << res[a[i]] << endl;
    return 0;
}