package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1024*1024), 1024*1024*10)

	if !scanner.Scan() {
		return
	}
	t, _ := strconv.Atoi(scanner.Text())
	
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	for ; t > 0; t-- {
		scanner.Scan()
		n, _ := strconv.Atoi(scanner.Text())
		counts := make(map[int]int64)
		var ans int64
		for i := 0; i < n; i++ {
			scanner.Scan()
			a, _ := strconv.Atoi(scanner.Text())
			ans += counts[a-i]
			counts[a-i]++
		}
		fmt.Fprintln(out, ans)
	}
}