BZOJ 2226 [Spoj 5971] LCMSum

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
using namespace std;
const int maxn=1000009;
const int u=1000000;
typedef long long Lint;


int T;
int n;

int cntprime;
int prime[maxn];
int vis[maxn];
Lint phi[maxn];
Lint f[maxn];
void Lineshake(){
	vis[1]=1;phi[1]=1;
	for(int i=2;i<=u;++i){
		if(!vis[i]){
			prime[++cntprime]=i;
			phi[i]=i-1;
		}
		for(int j=1;(j<=cntprime)&&(i*prime[j]<=u);++j){
			vis[i*prime[j]]=1;
			if(i%prime[j]==0){
				phi[i*prime[j]]=phi[i]*prime[j];
				break;
			}
			phi[i*prime[j]]=phi[i]*(prime[j]-1);
		}
	}
	phi[1]=1;
	for(int i=2;i<=u;++i)phi[i]=phi[i]*1LL*i/2;
}

void minit(){
	cntprime=0;
	memset(vis,0,sizeof(vis));
}

int main(){
	scanf("%d",&T);
	minit();
	Lineshake();
	for(int d=1;d<=u;++d){
		for(int k=1;k*d<=u;++k){
			f[d*k]+=phi[d]*d*k;
		}
	}
	while(T--){
		scanf("%d",&n);
		printf("%lld\n",f[n]);
	}
	return 0;
}