On subsets of integers having dense orbits

Zhuowen Guo, Jiahao Qiu, Hui Xu +1

Let $A\subset \mathbb{N}$. We say $A$ is an $R$-sequence for a given minimal system $(Y,S)$ if there is $y\in Y$ such that $\{S^{n}y:n\in A\}$ is dense in $Y$. Richter asked if $A$ i…