题目描述
You are given an array $a_1, a_2 \dots a_n$. Calculate the number of tuples $(i, j, k, l)$ such that:
- $1 \le i < j < k < l \le n$;
- $a_i = a_k$ and $a_j = a_l$;
Input
The first line contains a single integer $t$ ($1 \le t \le 100$) — the number of test cases.
The first line of each test case contains a single integer $n$ ($4 \le n \le 3000$) — the size of the array $a$.
The second line of each test case contains $n$ integers $a_1, a_2, \dots, a_n$ ($1 \le a_i \le n$) — the array $a$.
It's guaranteed that the sum of $n$ in one test doesn't exceed $3000$.
Output
For each test case, print the number of described tuples.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
样例输出
提示
In the first test case, for any four indices $i < j < k < l$ are valid, so the answer is the number of tuples.
In the second test case, there are $2$ valid tuples:
- $(1, 2, 4, 6)$: $a_1 = a_4$ and $a_2 = a_6$;
- $(1, 3, 4, 6)$: $a_1 = a_4$ and $a_3 = a_6$.