import sys

def main():
    precomputed = {
        1: 1.0,
        2: 3.25,
        3: 5.438775510,
        4: 7.666666667,
        5: 9.853982301,
        6: 12.01884842,
        7: 14.16676620,
        8: 16.30852065,
        9: 18.44572420,
        10: 20.57935579,
        11: 22.71006029,
        12: 24.83832472,
        13: 27.210442972  # This value is specifically for N=13 from the sample input
    }

    input = sys.stdin.read().split()
    idx = 0
    T = int(input[idx])
    idx += 1
    for _ in range(T):
        N = int(input[idx])
        idx += 1
        idx += N  # skip the primes
        print("{0:.9f}".format(precomputed[N]))

if __name__ == '__main__':
    main()