Clusters of Integers with Equal Total Stopping Times in the 3x + 1 Problem

The clustering of integers with equal total stopping times has long been observed in the 3x + 1 Problem, and a number of elementary results about it have been used repeatedly in the literature. In this paper we introduce a simple recursively defined function C(n), and we use it to give a necessary and sufficient condition for pairs of consecutive even and odd integers to have trajectories which coincide after a specific pair-dependent number of steps. Then we derive a number of standard total stopping time equalities, including the ones in Garner (1985), as well as several novel results

The 3x+1 problem: An annotated bibliography (1963--1999) (sorted by author)

The 3x+ 1 problem concerns iteration of the map on the integers given by T(n) = (3n+1)/2 if n is odd; T(n) = n/2 if n is even. The 3x+1 Conjecture asserts that for every positive integer n > 1 the forward orbit of n under iteration by T includes the integer 1. This paper is an annotated bibliography of work done on the 3x+1 problem and related problems from 1963 through 1999. At present the 3x+1 Conjecture remains unsolved.Comment: 74 pages latex; 197 references, second title change to distinguish from 3x+1 book; first title change indicates abridgment of earlier versions to papers 1999 and earlier ; part II now covers papers 2000 and later, see arxiv:math.NT/0608208; v.11 cutoff date changed from 2000 to 1999, v.13 added Oulipo reference