#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
    A[i]--;
  }
  vector<int> cnt(2000, 0);
  vector<vector<int>> cnt2(2000, vector<int>(2000, 0));
  long long ans = 0;
  for (int i = N - 1; i >= 0; i--){
    for (int j = 0; j < i; j++){
      int k = A[i] - A[j] - 10;
      if (k > 0){
        int c = A[i] - k;
        int d = c + k + 1;
        if (0 <= c && c < 2000 && 0 <= d && d < 2000){
          ans += cnt2[c][d];
        }
      }
    }
    for (int j = 0; j < 2000; j++){
      cnt2[A[i]][j] += cnt[j];
    }
    cnt[A[i]]++;
  }
  cout << ans << endl;
}