Monks, Kenneth G. - 3x+1 Minus the +

dmtcs:297 - Discrete Mathematics & Theoretical Computer Science, January 1, 2002, Vol. 5
3x+1 Minus the +

Authors: Monks, Kenneth G.

We use Conway's \emphFractran language to derive a function R:\textbfZ^+ → \textbfZ^+ of the form R(n) = r_in if n ≡ i \bmod d where d is a positive integer, 0 ≤ i < d and r_0,r_1, ... r_d-1 are rational numbers, such that the famous 3x+1 conjecture holds if and only if the R-orbit of 2^n contains 2 for all positive integers n. We then show that the R-orbit of an arbitrary positive integer is a constant multiple of an orbit that contains a power of 2. Finally we apply our main result to show that any cycle \ x_0, ... ,x_m-1 \ of positive integers for the 3x+1 function must satisfy \par ∑ _i∈ \textbfE \lfloor x_i/2 \rfloor = ∑ _i∈ \textbfO \lfloor x_i/2 \rfloor +k. \par where \textbfO=\ i : x_i is odd \ , \textbfE=\ i : x_i is even \ , and k=|\textbfO|. \par The method used illustrates a general mechanism for deriving mathematical results about the iterative dynamics of arbitrary integer functions from \emphFractran algorithms.

Volume: Vol. 5
Published on: January 1, 2002
Submitted on: March 26, 2015
Keywords: discrete dynamical systems,Collatz Conjecture,3x+1 problem,Fractran,[INFO.INFO-DM] Computer Science [cs]/Discrete Mathematics [cs.DM]


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