#include <bits/stdc++.h>
using namespace std;
const int MAX = 200;
int main(){
  cout << fixed << setprecision(20);
  vector<vector<long double>> dp(MAX + 1, vector<long double>(MAX + 1, 0));
  dp[0][0] = 1;
  for (int i = 0; i < MAX; i++){
    for (int j = 1; j <= i; j++){
      dp[i + 1][j - 1] += dp[i][j] * j;
      dp[i + 1][j + 1] += dp[i][j] * j;
    }
    for (int j = 0; j <= i; j++){
      dp[i + 1][j + 1] -= dp[i][j] * 2 * (i + 1);
    }
  }
  int T;
  cin >> T;
  for (int i = 0; i < T; i++){
    int N;
    long double x;
    cin >> N >> x;
    long double s = 0;
    for (int j = N; j >= 0; j--){
      s = s * x + dp[N][j];
    }
    s *= pow(x * x + 1, -(long double) N / 2);
    for (int j = 1; j <= N; j++){
      s /= j;
    }
    cout << s << endl;
  }
}