#include<cstdio>
#include<cstring>
#include<algorithm>
#include<map>
#include<vector>
using namespace std;
#define maxN 305
#define lson i<<1
#define rson (i<<1)+1
#define piii pair<int,pair<int,int> >
#define pii pair<int,int>
#define F first
#define S second
#define mkp(a,b) make_pair(a,b)
#define pb(x) push_back(x)
typedef long long LL;
int a[maxN];
int main()
{
    int T,N;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&N);
        for(int i=1;i<=N;i++) scanf("%d",&a[i]);
        int num = 0;
        for(int i=1;i<=N;i++)
            for(int j=1;j<=N;j++)
                if(a[i]>a[j])
                    num++;
        double base = 1.0*N*(N-1);
        printf("%lf\n",1.0*num/base);
    }
    return 0;
}