#include<bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include"debug.h"
#else
#define debug(...) void()
#endif
#define all(x) (x).begin(),(x).end()
template<class T>
auto ary(T *a,int l,int r){
	return vector<T>{a+l,a+1+r};
}
using ll=long long;
using ull=unsigned ll;
int T,n,k;
double frac(int n){
	if(!n)return 0;
	return n*(log(n)-1)+1;
}
double C(int n,int k){
	return frac(n)-frac(k)-frac(n-k);
}
double calc(int n,int k){
	k=min(k,n*2/3);
	return log(2)*k+C(n,k);
}
void get(){
	scanf("%d%d",&n,&k);
	printf("%.10lf\n",log(3ll*k+1)+log(3)*n-calc(n,k));
}
int main(){
	for(scanf("%d",&T);T--;)get();
	return 0;
}
#ifdef DEBUG
#include"debug.hpp"
#endif