How many flips would it take to get a sequence of HTHT?

There's a general formula for the expected number of flips to get any sequence [math]S[/math] of fair coin flips, which depends on how much the end of [math]S[/math] overlaps the beginning of [math]S[/math]. read more

There’s a general formula for the expected number of flips to get any sequence [math]S[/math] of fair coin flips, which depends on how much the end of [math]S[/math] overlaps the beginning of [math]S[/math]. read more

and the expected number of flips are [20, 18, 16, 10]. That is from initial state it will take 20 flips. Starting from H will be 18. read more