3x + 1 problem Articles The Recursive Stopping Time Structure of the 3x + 1 function (2017), latest update linkNew results on the stopping time behaviour of the Collatz 3x + 1 function (2015)The Role of the Fibonacci Sequence in the Collatz 3n + 1 Function (2014)On the structure and the behaviour of Collatz 3n + 1 sequences (2014) Directed Collatz graphs Special tree structure up to 341Special tree structure up to column 6