a fair 2 sided coin is flipped 4 times . what is the probability that tails will be the result at least twice , but not more than 4 times ?
n0 = 2.0
n1 = 4.0
n2 = 4.0
t0 = n0**min(n1, 5)
t1 = 1 / t0
t2 = t1 + t1
t3 = n1 * t1
t4 = t2 + t3
answer = 1.0 - t4
print(answer)