Question: You are in a strange multi floor shopping mall. What's strange about it is the placement of the escalators. For every floor (except the first and second) there are two escalators that go down a single floor and three escalators that go down two floors at once, without letting shoppers get off at the intermediate floor. (The first floor has no down escalators, and the second floor has the expected two escalators that go down a single floor.) This makes navigation somewhat confusing. Still, for an n-floor shopping mall, how many ways are there to get from the top floor to the first floor so you can leave?