The Suspiciously Even Log

A pit boss rolls a fair six-sided die over and over, stopping at the first 6 6 , and a machine logs the whole sequence. Later, an auditor reads the log and reports one fact: every roll in the sequence — including the final 6 6 — was an even number. Given that report, what is the expected length of the logged sequence? (Warning: the answer is not 3 3 .)

Answer

Free accounts unlock one worked solution a day. Pro includes every answer.