#include <iostream>
#include <cstdio>
using namespace std;
int a[310];
int main()
{
    int T, n;
    scanf("%d", &T);
    while (T--) {
        cin >> n;
        for (int i = 0; i < n; i++) {
            scanf("%d", &a[i]);
        }
        int cnt = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                if (a[j]>a[i]) {
                    cnt++;
                }
            }
        }
        printf("%.6f\n", cnt*1.0/(n*(n-1)));
    }
    return 0;
}