欧拉筛

#include <bits/stdc++.h>
#define lld long long
using namespace std;
int n, a[100005], f[100005];
vector<int>sum;

int main() {
	cin >> n;
	for (int i = 2; i <= n; i++) {
		a[i] = i;
	}
	for (int j = 2; j <= n; j++) {
		if (f[j] == 0)
			sum.push_back(j);
		for (int i = 0; i <= sum.size() && sum[i]*j <= n; i++) {
			f[j * sum[i]] = 1;
			if (j % sum[i] == 0)
				break;
		}
	}
	for (int i = 0; i < sum.size(); i++) {
		cout << sum[i] << ' ';
	}

	return 0;
}