A month ago I posted a question. It was viewed by about 50 people, received one comment (for which I am grateful), and no answer, not even an attempt at an answer. I suspect this is because the question was more postgraduate head scratcher and less high school maths homework. Can someone suggest a forum where I can post my question and get, if not an answer, at least some sort of useful feedback? Thanks in advance.
Original post: https://math.stackexchange.com/questions/4103273/cardn-cardn
Note: This is a general question but I have no idea how to tag it as such.