The real challenge is if I give you an arbitrary list of numbers, without explaining to you the process that constructed them. In that case, you will quickly find it is impossible to solve, even for very short lists.
Take, for example, this list: Open Challenge to ID Advocates. It is framed differently, but we can repose the problem. What is the optimal compression of those five sequences? Not an easy thing to solve. In fact, as we’ve seen, you cannot figure it out. I’m almost guaranteed (because I produced the numbers) to be able to come up with a better compression than you. However, even that is not guaranteed to be optimal. There might be a better compression I did not envision. It is an undecidable problem.