#nullable enable

#region
var _input = Array.Empty<string>();
var _iter = 0;
string String()
{
    while (_iter >= _input.Length) (_input, _iter) = (Console.ReadLine()!.Split(' '), 0);
    return _input[_iter++];
}
T I<T>() where T : IParsable<T> => T.Parse(String(), null);
#endregion

T[] Range<T>(int n, Func<T> F) => Enumerable.Range(0, n).Select(_ => F()).ToArray();

var n = I<int>();
var az = Range(n, I<int>);
var ans = 0L;
var bag = new Bag<(long, int)>();
for (var i = 1; i <= n; i++)
{
    var a = az[i - 1];
    var d = 0L;
    for (var k = 1; k <= n; k++)
    {
        d += i;
        if (d > 200000) break;
        var v = d - a;
        if (bag[(v, k)] > 0)
        {
            ans += bag[(v, k)];
        }
        bag.Add((-v, k));
    }
}
Console.WriteLine(ans);

class Bag<K> where K : notnull
{
    readonly Dictionary<K, int> _dictionary = new();
    public void Add(K key)
    {
        var dictionary = _dictionary;
        if (dictionary.TryGetValue(key, out var count)) dictionary[key] = count + 1;
        else dictionary[key] = 1;
    }
    public bool Remove(K key)
    {
        var dictionary = _dictionary;
        if (!dictionary.TryGetValue(key, out var count)) return false;
        if (count == 1) dictionary.Remove(key);
        else dictionary[key] = count - 1;
        return true;
    }
    public int this[K key] => _dictionary.TryGetValue(key, out var count) ? count : 0;
    public int CountKeys => _dictionary.Count;
}