#include <string>
#include <iostream>
#include <cstdio>
#include <map>

using namespace std;

#define N 305
int arr[N];

int main() {
    int test, n;
    scanf("%d", &test);
    for (int cas = 1; cas <= test; cas++) {
        scanf("%d", &n);
        for (int i = 0; i < n; i++)
            scanf("%d", arr + i);
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (j == i) continue;
                if (arr[i] < arr[j]) {
                    cnt++;
                }
            }
        }
        double res = (double)cnt / (n * (n - 1));
        printf("%.6f\n", res);
    }
    return 0;
}