Suppose you roll a six-sided die n times and record the sequence of results. For example you might roll the die three times and get 2 on your first roll, 5 on your second roll and 6 on your third roll. In that case the sequence would be 2, 5, 6. Derive a formula on n that counts the number of different sequences in which there is at least one '6'. Explain clearly why your formula works. Also, make sure your formula is as simple as possible.