I have recently come across an interesting problem Czarnowski's cat function, which is discussed by Ninosław Brzostowiecki here: https://www.youtube.com/watch?v=3I32lpziDt8.
Some more lore about the function is described at A question regarding Czarnowski's cat function, but it appears that this is just a homework problem and not the unsolved problem about the function. This is not homework.
Is there any more info about the current state of research on the function? Most sources point to the function being discovered in 1896, but http://www.svc.edu/index_to_mathematical_problems_1980_1984_indexes_to_mathematical_problems.pdf link seems to suggest that there was a development from 1980-1984. Unfortunately, clicking on the link will take you to a paywall.
