#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = s; i < (ll)(t); i++)
#define all(x) begin(x), end(x)

template <class T> bool chmin(T& x, T y) {
	return x > y ? (x = y, true) : false;
}
template <class T> bool chmax(T& x, T y) {
	return x < y ? (x = y, true) : false;
}

struct io_setup {
	io_setup() {
		ios::sync_with_stdio(false);
		cin.tie(nullptr);
		cout << fixed << setprecision(15);
	}
} io_setup;

void solve() {
	int n;
	cin >> n;
	vector<int> a(n);
	rep(i, 0, n) cin >> a[i];
	constexpr int sq = 448;
	int sqn = min(n, sq);
	ll ans = 0;
	rep(i, 0, sqn) rep(j, i + 1, sqn) {
		if ((a[i] + a[j]) % (i + j + 2) == 0) ans++;
	}
	int shf = 2e5;
	array<vector<int>, sq> mp;
	mp.fill(vector<int>(shf * 2 + 1, 0));
	rep(i, 0, sqn) {
		ll tmp = i + 1 - a[i];
		rep(k, 0, sqn) {
			mp[k][shf + tmp]++;
			tmp += i + 1;
		}
	}
	rep(i, sqn, n) {
		ll tmp = i + 1 - a[i];
		rep(k, 0, sqn) {
			if (tmp > shf) break;
			ans += mp[k][shf - tmp];
			mp[k][shf + tmp]++;
			tmp += i + 1;
		}
	}
	cout << ans << "\n";
}

int main() {
	int t = 1;
	// cin >> t;
	while (t--) solve();
}