A coin is tossed until the same result appears twice in a row. Find the probability that the coin is tossed less than 6 times.
I have to solve it using Bernulli trials but I cannot get the answer right.
$P(k)=\left(\begin{array}{l}n \\ k\end{array}\right) p^k q^{n-k}$
It didn't help reading the same question asked earlier. Answers differ slightly
The right answer is $\frac{15}{16}$, according to this website where it is the 6.2.a excercise
I considered $n=6, k = 2, p= 0,5.$ Computing those values I don't get the desired answer