Open problems that are understandable with knowledge from Calculus 3

Question

I like to know what open problems have statements that are understandable for someone with knowledge of Calculus 3?

For example, with a little work, the Jacobian Conjecture might be accessible.

Answer 1

The Kolakoski sequence $(K_n) $ with

$K_n\in \{1,2\} $.

it looks like

$K=12211212212211211221211... $

it is defined by the fact that $K $ is a fixed point of the RLC ( run length encoding).

The open question asks if, asymptotically speaking, there are as many $1$ as $2$ symbols.