It’s a dark panel in a dark elevator, so I’m not sure how well you can see the details, but this is the elevator panel in the hotel where Barbara and I have been staying in NYC. The puzzle is the numbering of the floors: why is there no 4th floor? And no 13th? (That one is easy.) And no 14th? And no 24th?
Perhaps the pattern in those numbers is obvious. Perhaps not. But the question remains: why those four? Why does a 22-floor hotel have floors that go up to 26, with four numbers missing?
I can think of certain students who would have a leg up in solving this puzzle.