What is the probability of flipping a coin and it coming up heads four times in a row

In a single toss, the probability that the result of the toss is head is 1/2:


For 2 tosses in a row, the probability that the result is head in both tosses is


If we continue, we find that the probability to have 4 heads in 4 consecutive tosses is given by

Iwould think that the correct answer is 8.1