#include <iostream>
#include <vector>
#include <numeric>
#include <unordered_map>
#include <cmath>
#include <algorithm>

void solve() {
    int N;
    std::cin >> N;

    std::vector<int> A(N);
    for (int i = 0; i < N; ++i) {
        std::cin >> A[i];
    }

    long long ans = 0;
    const int acm = 200000;

    int B = static_cast<int>(cbrt(2.0 * acm * acm / std::max(1, N)));
    if (B == 0) B = 1;

    for (int k = 1; k <= B; ++k) {
        std::unordered_map<long long, int> freq;
        for (int i = N; i >= 1; --i) {
            long long val_i = (long long)A[i - 1] - (long long)k * i;
            long long target = -val_i;
            if (freq.count(target)) {
                ans += freq[target];
            }
            freq[val_i]++;
        }
    }

    const int S_limit = (acm + acm) / (B + 1);

    for (int i = 1; i <= N; ++i) {
        if (2 * i + 1 > S_limit) {
            break;
        }
        for (int j = i + 1; j <= N; ++j) {
            int s = i + j;
            if (s > S_limit) {
                break;
            }
            long long sum_A = (long long)A[i - 1] + A[j - 1];
            if (sum_A % s == 0) {
                if (sum_A / s > B) {
                    ans++;
                }
            }
        }
    }

    std::cout << ans << std::endl;
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(0);
    solve();
    return 0;
}