Alice doesn't like the digits 3,7 and 9. If a number with n digits contains 3,7 and 9 at the same time, then Alice considers this to be a very unlucky number. For example, if say n=5, then 69637 is an unlucky number since it has 3,7 and 9 as digits. A number like 64637 is NOT unlucky since it is missing 9. A number like 02379 is not a 5 digit number. So we don't even consider it. Find the total number of numbers with n digits that Alice considers to be very unlucky. The final answer should be a function of just n. You don't have to simplify this.