选出来的个数能凑成
或者
必然有一个性质,
。
$$
#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
const int N = 2e7 + 10;
int prime[N], cnt;
ull mu[N];
bool st[N];
void init() {
mu[1] = 1;
for (int i = 2; i < N; i++) {
if (!st[i]) {
prime[++cnt] = i;
mu[i] = -1;
}
for (int j = 1; j <= cnt && 1ll * i * prime[j] < N; j++) {
st[i * prime[j]] = 1;
if (i % prime[j] == 0) {
break;
}
mu[i * prime[j]] = -mu[i];
}
}
for (int i = 1; i < N; i++) {
mu[i] += mu[i - 1];
}
}
map<ll, ull> mp;
ull Djs_mu(ll n) {
if (n < N) {
return mu[n];
}
if (mp.count(n)) {
return mp[n];
}
ull ans = 1;
for (ll l = 2, r; l <= n; l = r + 1) {
r = n / (n / l);
ans -= (r - l + 1) * Djs_mu(n / l);
}
return mp[n] = ans;
}
ull quick_pow(ull a, ll n) {
ull ans = 1;
while (n) {
if (n & 1) {
ans = ans * a;
}
a = a * a;
n >>= 1;
}
return ans;
}
int main() {
// freopen("in.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
init();
ull n, m, ans = 0;
cin >> n >> m;
for (ull l = 1, r; l <= m; l = r + 1) {
r = m / (m / l);
ans += quick_pow(m / l, n) * (Djs_mu(r) - Djs_mu(l - 1));
}
cout << ans << "\n";
return 0;
} 
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