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

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    ll N;
    cin>>N;
    int MX=0;
    ll an=0;
    vector<int> D(N);
    for(int i=0;i<N;i++){
    	cin>>D[i];
    	MX=max(MX,D[i]);
    }
    MX+=MX;
    unordered_map<ll,ll> M;
    for(ll i=1;i<=N;i++){
        ll A=D[i-1];
        // cin>>A;
        for(ll k=1;k*i<=MX;k++){
            ll d=A-i*k;
            ll e=k*ll(2e9)+d;
            ll f=k*ll(2e9)-d;
            // cout<<i<<" "<<k<<" "<<e<<" "<<f<<endl;
            if(M.count(f))an+=M[f];
            M[e]++;
        }
    }    
    cout<<an<<"\n";
}