#include<bits/stdc++.h>
using namespace std;

int main(){
  using ll=long long;
  int m=4e5;
  int n;
  cin>>n;
  vector<int> a(n);
  for (int i=0;i<n;i++) cin>>a[i];
  ll ans=0;
  vector<vector<int>> vec(m+1);
  for (int i=0;i<n;i++){
    for (int j=0;j*(i+1)<=m;j++){
      ll val=a[i]-(i+1)*j;
      vec[j].push_back(val);
    }
  }
  for (auto v:vec){
    map<int,int> mp;
    for (int x:v){
      ans+=mp[-x];
      mp[x]++;
    }
  }
  cout<<ans<<endl;
}