use std::collections::HashMap;
use std::io::{self, BufRead};

fn main() {
    // 入力読み込み
    let stdin = io::stdin();
    let mut lines = stdin.lock().lines();

    let n: usize = lines.next().unwrap().unwrap().trim().parse().unwrap();
    let a: Vec<i32> = lines
        .next()
        .unwrap()
        .unwrap()
        .split_whitespace()
        .map(|s| s.parse().unwrap())
        .collect();

    let max_a = *a.iter().max().unwrap();
    let offset = max_a as usize;

    // dp[b + offset][m] の形で管理
    let mut dp: Vec<HashMap<i32, i64>> = vec![HashMap::new(); 2 * offset + 1];

    let mut answer: i64 = 0;

    for (i, &val) in a.iter().enumerate() {
        let i0 = (i + 1) as i32;

        // answer 計算
        let mut b = -val + i0;
        let mut m = 1;
        while b <= max_a {
            let index = (b + offset as i32) as usize;
            if let Some(&count) = dp[index].get(&m) {
                answer += count;
            }
            b += i0;
            m += 1;
        }

        // dp 更新
        let mut b = val - i0;
        let mut m = 1;
        while b >= -max_a {
            let index = (b + offset as i32) as usize;
            *dp[index].entry(m).or_insert(0) += 1;
            b -= i0;
            m += 1;
        }
    }

    println!("{}", answer);
}