#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

using namespace std;

int a[310], vis[310];

void k(int left, int right)
{
    int i, j, t, temp;
    if (left > right)
        return ;
    temp = a[left];
    i = left;
    j = right;
    while (i != j)
    {
        while (a[j] >= temp && i < j)
            j--;
        while (a[i] <= temp && i < j)
            i++;
        if (i < j)
        {
            t = a[i];
            a[i] = a[j];
            a[j] = t;
        }
    }
    a[left] = a[i];
    a[i] = temp;
    k(left, i - 1);
    k(i + 1, right);
}

int C(int n, int m)
{
    int s;
    if (n == 1)
        s = 1;
    else if (m == 0)
        s = 1;
    else if (n == m)
        s = 1;
    else
        s = C(n - 1, m - 1) + C(n - 1, m);
    return s;
}

int main()
{
    double f;
    int t;
    scanf("%d", &t);
    while (t--)
    {
        int n;
        scanf("%d", &n);
        for (int i = 1; i <= n; i++)
            scanf("%d", &a[i]);
        k(1, n);
//        memset(vis, 0, sizeof(vis));
//        for (int i = 1; i <= n; i++)
//            for (int j = i + 1; j <= n; j++)
//                if (a[i] == a[j])
//                    vis[j] = 1;
//            for (int i = 1; i <= n; i++)
//                printf("%d ", a[i]);
        int flag = 0;
        for (int i = n; i >= 1; i--)
            for (int j = i - 1; j >= 1; j--)
            {
                if (a[i] > a[j])
                    flag++;
            }
        f = flag * 1.0 / (C(n, 2) * 2);
//    printf("%d\n", C(n, 2));
        printf("%.6lf\n", f);
    }
    return 0;
}