The 3x+1 Problem: An Overview
arXiv:2111.02635
Abstract
This paper is an overview and survey of work on the 3x+1 problem, also called the Collatz problem, and generalizations of it. It gives a history of the problem. It addresses two questions: (1) What can mathematics currently say about this problem? (as of 2010). (2) How can this problem be hard, when it is so easy to state?
27 pages; page breaks and stylefile differ from published version; some typos corrected, journal references updated