[Haskell-beginners] exercises/examples for streams

Hello, I'm preparing for an exam (university level introductory course). Functional programming in Haskell is part of it. That includes the concept of streams (theoretically infinite list computations). I have difficulties in solving exercises that ask me to define streams for a given problem. Do you know good examples, the difficulty should be maybe a little harder than Fibonacci or intersections, but solvable in about 5 to 10 minutes. If there are examples from the book "Haskell - the craft of functional programming", please don't spoiler, I'm reading it parallel to this conversation. Don't give solutions, just problems (5 to 10 more will do). Examples, other than integer sequences are welcome. Pascal