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

using isize = size_t;
using i32 = int;
using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128_t;
using u128 = __uint128_t;
using f64 = long double;
using p2 = pair<i64, i64>;
using el = tuple<i64, i64, i64>;
using mint = atcoder::modint998244353;

void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(18);
  _main();
}

i64 pow(i64 x, i64 n) {
  i64 res = 1;
  i64 t = x;
  while (n > 0) {
    if (n & 1) res *= t;
    t *= t;
    n >>= 1;
  }
  return res;
}

void _main() {
  i64 n;
  cin >> n;
  vector<i64> a(n + 1);
  for (i64 i = 1; i <= n; i++) {
    cin >> a[i];
  }
  i64 m = 300;
  vector<i64> cnt(m * n + 200010, 0);
  i64 base = m * n;
  i64 ans = 0;
  for (i64 k = 1; k < m; k++) {
    i64 c = 0;
    for (i64 i = 1; i <= n; i++) {
      i64 x = a[i] - i * k;
      i64 y = -x;
      ans += cnt[y + base];
      c += cnt[y + base];
      cnt[x + base]++;
    }
    for (i64 i = 1; i <= n; i++) {
      i64 x = a[i] - i * k;
      cnt[x + base]--;
    }
  }
  for (i64 i = 1; i <= n; i++) {
    if (i * m > 400000) break;
    for (i64 j = i + 1; j <= n; j++) {
      if ((i + j) * m > 400000) break;
      i64 s = a[i] + a[j];
      if (s % (i + j) == 0 && s / (i + j) >= m) ans++;
    }
  }
  cout << ans << "\n";
}