#include<cstdio>

#define MAXN 201

int a[MAXN];

int main(){
    int _; scanf("%d",&_);
    while(_--){
        int n;scanf("%d",&n);
        for(int i=1;i<=n;++i)scanf("%d",&a[i]);
        int ans=0;
        for(int i=1;i<=n;++i)
            for(int j=1;j<=n;++j){
                if(i==j)continue;
                if(a[i]>a[j])ans++;
            }
        printf("%.6lf\n",(double)ans/(n*(n-1)));
    }
}