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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n;
    cin >> n;
    vector<int> a(n);
    for(auto &&v : a) cin >> v;
    auto b = a.begin() - 1;
    ll ans = 0;
    for(int d = 1; d <= n; d++){
        int m = min(n, (n / d) * 3);
        unordered_map<int, int> mp;
        for(int i = 1; i <= m; i++){
            int lv = b[i] - i * d;
            ans += mp[-lv];
            mp[lv]++;
        }
    }
    cout << ans << '\n';
}