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2497-Eratosthenes.cpp
63 lines (58 loc) · 1.18 KB
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2497-Eratosthenes.cpp
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#include <bits/stdc++.h>
#define MAXN 10000005
using namespace std;
const int M=1e9+7;
int T,n,S[MAXN];
int prime[MAXN],phi[MAXN],mu[MAXN],tot;
bool not_prime[MAXN];
inline void fadd(int &x,int y){x+=y;if (x>=M) x-=M;return ;}
inline int sqr(int x){return 1LL*x*x%M;}
inline int f(int x){return 1LL*x*(x+1)/2%M;}
inline void EratosthenesShaker(int n)
{
phi[1]=mu[1]=1;
for (int i=2;i<=n;i++)
{
if (!not_prime[i])
{
prime[++tot]=i;
phi[i]=i-1;mu[i]=-1;
}
for (int j=1;i*prime[j]<=n;j++)
{
not_prime[i*prime[j]]=true;
if (!(i%prime[j]))
{
mu[i*prime[j]]=0;
phi[i*prime[j]]=phi[i]*prime[j];
break;
}
mu[i*prime[j]]=-mu[i];
phi[i*prime[j]]=phi[i]*(prime[j]-1);
}
}
for (int i=1;i<=n;i++) fadd(mu[i],M);
for (int i=1;i<=n;i++)
for (int j=1;j*i<=n;j++)
fadd(S[i*j],1LL*mu[i]*phi[j]%M);
for (int i=1;i<=n;i++) S[i]=1LL*S[i]*sqr(i)%M;
for (int i=1;i<=n;i++) fadd(S[i],S[i-1]);
return ;
}
int main()
{
EratosthenesShaker(10000000);
scanf("%d",&T);
while (T--)
{
scanf("%d",&n);int ans=0;
for (int l=1,r;l<=n;l=r+1)
{
r=n/(n/l);
int t=S[r];fadd(t,M-S[l-1]);
t=1LL*t*sqr(f(n/l))%M;fadd(ans,t);
}
printf("%d\n",ans);
}
return 0;
}