G15 威尔逊定理

 视频链接：https://www.bilibili.com/video/BV1GG411n7tW/

 HDU 2973 YAPTCHA

#include <iostream>
using namespace std;

typedef long long LL;
const int N = 1000001;
const int mx = 3000008;
int s[N],p[N],vis[mx],t,n;

void get_prim(){
  for(LL i = 2; i < mx; ++i)
    if(!vis[i]){
      if((i-7)%3 == 0) 
        p[(i-7)/3] = 1;
      for(LL j=i*i; j<mx; j+=i) 
        vis[j] = 1;
    }
}
int main(){
  get_prim();
  for(int i=2; i<N; ++i)
    s[i] = s[i-1]+p[i];
  scanf("%d", &t);
  while(t--){
    scanf("%d", &n);
    printf("%d\n", s[n]);
  }
}