Dynamics of the iterated map $n \to 3n+1$ if $n$ is odd and $n \to \frac n2 $ if $n$ is even. Generalizations to $n \to 3n-1 $ or $ n \to 5n+1$ or even to $n \to pn+q$ . Other names are "$3x+1$-problem","syracuse problem". If you have a question, please be specific to your detail. MSE is not ...

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counting steps in Collatz Sequence [closed]

I'm tring to code a Java code to find the collatz sequence of a given integer. In the given problem I have they've given $6 \rightarrow 6\: 3\: 10\: 5\: 16\: 8\: 4\: 2$ It has taken $14$ steps to ...
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Applying Collatz function iterations to large integers

Given the Collatz function and its iterates: $$ T(n) = \begin{cases} n/2, & \text{if $n$ is even} \\ (3n+1)/2, & \text{if $n$ is odd} \end{cases} $$ and $$ T^{k}(n) = T(T^{k-1}(n)).$$ How ...
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The longest known cycle length of generalized collatz $5x+1$ trajectory

The generalized collatz $5x+1$ trajectory, if $n$ is even then divide $n$ by $2$, and if $n$ odd then multiply $n$ by $5$ and then add $1$. For example if $n=3$, we have ...
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Prime Factorization patterns of $\sum_{i=0}^k{4^i}$

$$ \text { Given the function: }f:\mathcal{N^+} \to \mathcal{N^+} where f \left(k\right) = \sum_{i=0}^k \,4^i. $$ Examining the prime factorizations of f(k) for k= 1...48, many factors appear in a ...
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Can Collatz's problem be used as a pseudo random prime sieve?

If you take the concept of $3x+1$, $\dfrac{x}{2}$ and starting at 2, create a tree. On the left nodes you apply the $3x+1$. On the right nodes, if the parent node is even apply the $\dfrac{x}{2}$. ...
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Partitions of the odd integers

Understanding the nature of the odd integers is a necessity to prepare oneself to work on the unsolved problems in number theory, such as the Collatz $3n+1$ problem. I hope to demonstrate how the ...
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1answer
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(Collatz) Modulo 18 Partitions of Collatz 3n+1 Trajectories

I have examined partial Collatz 3n+1 trajectories going from one odd integer to the next. These lead to an infinite number of repeated patterns where the "next" odd integer is congruent to one of ...
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Collatz $4n+1$ rule?

I noticed something about the Collatz Conjecture, (I was literally obsessed with trying to prove it). I of course have NO intention of trying to prove it, clearly it is beyond my reach and I hope not ...
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Collatz Conjecture: Literature on Convergence

Does anyone know of a paper showing that if all n converge, they must converge to unity for n>0. Else, any literature related to convergence properties would be appreciated. Thanks, Jordan
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Collatz Conjecture Algorithm

Related: A general question about the Collatz Conjecture and finding that integer that doesn't work I was coding a solution to the $3k+1$ problem and was looking at ways to speed up the computation. ...
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Generalizations of the Collatz to $(mx \pm 1)/2$ for $m=181$ gives two nontrivial cycles; are more examples $m$ known?

Generalizing the Collatz $T_{3,+}(n) = \left\{ \begin{array} {cl} {3n+1 \over 2} & \text{ when } n=2k+1 \\ \frac n{2^B} & \text{with maximal } B \gt 0 \text{ where } 2^B | n \end{array} ...
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Can any functions be expressed in one formula? (without conditions)

This is the extension of my previous inquiry: Is it possible to describe the Collatz function in one formula? Can each of all functions be expressed in one formula? That is, can any function ...
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Is the 3x+1 problem solved? [closed]

I found an article by Peter Schorer from June 29,2015 which is claming to give a solution of the 3x+1 problem. Are there remarks from any mathematicians if this is correct or not?
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Collatz-type problems with known divergent trajectories

It is a well-known problem, known as Collatz problem, to determine whether iteratively applying the map $f(x)=\frac{x}{2}\text{ if $x$ is even and }f(x)=3x+1\text{ otherwise}$ on a positive integer ...
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collatz with choice

I was wondering what would become of the Collatz problem if, instead of taking the map 3n+1 for odd integers only, one could consider both paths associated with maps n/2 and 3n+1 for even integers (so ...
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Does this extension of the Collatz sequence converge for n=550?

The Collatz function, or $3n + 1$ function is well known. A heuristic argument that most inputs should converge with repeated application of the function is as follows. With probability 1/2 an input ...
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Is it possible to describe the Collatz function in one formula?

This is related to Collatz sequence, which is that $$C(n) = \begin{cases} n/2 &\text{if } n \equiv 0 \pmod{2}\\ 3n+1 & \text{if } n\equiv 1 \pmod{2} .\end{cases}$$ Is it possible to describe ...
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Could this odd insight help explain part of the difficulty in proving the Collatz Conjecture?

Background: Here's a crash course on the Collatz Conjecture. Basically, you take a number and if it is even you divide it by two. If a number is odd, you multiply it by three and then add one. You ...
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1answer
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Is the Collatz function piecewise linear?

I read somewhere that the Collatz function $\mathbb Z \rightarrow \mathbb Z$: $$\text{Collatz}(x) = \begin{cases} x/2 &&x \; \mathrm{even} \\ 3x+1 &&x \; \mathrm{odd}\end{cases}$$ is ...
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Besides the $3x + 1$ problem, for which similar problems are still unresolved regarding trayectory?

Generalize the $3x + 1$ problem as $cx \pm 1$, where $c$ is a positive odd integer and $x$ is a positive integer iterated through the function as far as possible to discover a cycle. If $x$ is even, ...
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Twin prime conjecture (Goldbach-Collatz remix)

Assuming Goldbach's conjecture, let's denote $r_{0}(n)$ for any integer $n$ greater than $1$ the smallest non negative integer $r$ such that both $n+r$ and $n-r$ are primes. Let $f$ be the map ...
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Uses of “Collatz induction”?

The Collatz conjecture is equivalent to the following "induction principle": If $P(0) \land P(1) \land (\forall{x} P(3 \cdot x + 2) \implies P(2 \cdot x + 1)) \land (\forall x P(x) \implies P(2 \cdot ...
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Looking for a verification or refutation my attempted proof of why the Collatz conjecture is probably false. [closed]

Most people think that the Collatz conjecture is true, but I think that I can prove the opposite. Let's make two functions, $f(x)$ and $g(x)$. $f(x) = $ The amount of numbers that can be solved in x ...
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966 views

Has the Collatz Conjecture been proven to be unprovable? [closed]

This paper, from a peer-reviewed journal, purports to prove that the Collatz Conjecture is unprovable. If it’s valid, why has it not received more attention? If it’s invalid, what is the flaw, and ...
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1answer
98 views

What causes long sequences of consecutive 'collatz' paths to share the same length?

I asked Longest known sequence of identical consecutive Collatz sequence lengths? some time ago, but I don't feel like it really got to the bottom of things. See, in the answers lopsy find a sequence ...
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Collatz algorithm generalization try-out (Collatz k-algorithm)

(Text Updated 2015/09/16, please see edit comments for changes) Recently I have been reading about the Collatz conjecture here in Mathematics Stack Exchange, and also found the fantastic paper of ...
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Trying mathematical induction with $3n+1$ conjecture

Collatz's Conjecture is also known as the $3n+1$ conjecture. Well I thought since the conjecture is dealing with natural numbers so we might as well try mathematical induction and see why it doesn't ...
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1answer
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A question about the $3n+1$ conjecture

So I know that if you take any even number $n$ that is a power of $2$ like $32 = 2^5,16=2^4$ or $64=2^6$ we will keep dividing by 2 until we reach 1. and so all the steps will be $\frac{n}{2}$ and we ...
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A general question about the Collatz Conjecture and finding that integer that doesn't work

I apologize if this question gets down-voted ahead of time. I've been working on the Collatz Conjecture all day with Python, because that is the language I'm most familiar with (I'm not a CS student, ...
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Consequences of Collatz Conjecture being true

Collatz conjecture has been conjectured for a long time and I think there are some evidence showing that it should be true. Similar to $P \neq NP$ conjecture, is there some interesting ...
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Is anything known about the size of the smallest number with stopping time $n$

Last couple of days I've been thinking about the Collatz conjecture, and now I wonder if any relation is known between $n$ and the smallest number with stopping time $n$. So for example, let's say ...
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In the Collatz function, why does $2^k-1$ reach $3^k-1$ after $2k$ steps, and could it be used to find divergent trajectories?

If you start calculating the Collatz function from an integer of the form $2^k-1$, you will reach $3^k-1$ after $2k$ steps. So, it is possible to pick a starting value that continuously zig-zags ...
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2answers
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In the Collatz function, why $3^{2k}-1$ and $3^{2k-1}-1$ always share the same trailing trajectory?

Why are the trajectories always the same for numbers of the form $3^{2k}-1$ and $3^{2k-1}-1$ for the Collatz function? For example, let $k = 3$. So, $3^6-1 = 728$ and $3^5-1 = 242$. The trajectories ...
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1answer
279 views

How could Collatz conjecture possibly be undecidable?

I wonder how the collatz conjecture could possibly be undecidable? Since let's say it's undecidable, then that means that no counter example can ever be found, and that to me seems to imply that non ...
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488 views

Collatz conjecture: Largest number in sequence with starting number n

This question is inspired by a CS course, and it only tangentially relates to the actual content of the exercise. Say in a hailstone sequence (Collatz conjecture) you start with a number n. For any ...
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263 views

Is this property of the Collatz sequence interesting?

As an amateur playing around with the Collatz conjecture, I've stumbled on something I haven't seen mentioned before, and that may or may not be noteworthy. Suggested by Gottfried Helms, here's a ...
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1answer
107 views

On a proof that “there are at least $F_n$ Collatz permutations of length $n$”.

Let $n, k \in \Bbb{N}$ and $F_n$ be the $n$th term of the Fibonacci sequence. Let $u$ be the map $x \to 3x+1$ and $d$ be the map $x \to \frac{x}{2}$. Let a type be a sequence of $u$'s and $d$'s. ...
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1answer
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What do these contour maps tell me about my Collatz expression?

I tested this limit on WolframAlpha, $$ \lim_{t\to\infty}\frac {2\ 3^r (2 t - 1) - 6} {3\ 2^r (2 t - 1) - 6}=\left(\frac{3}{2}\right)^{r-1},$$ which displayed two contour maps: . Can ...
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1answer
58 views

How to find the integer solutions of $\frac{2^m-1}{2^{m+x}-3^x}=2a+1$? [duplicate]

Is there a way to find all integer triplets of $(x, m, a)$ for the following equation. $$\frac{2^m-1}{2^{m+x}-3^x}=2a+1$$
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Number of possible cycles in collatz conjecture

I had been following all the blogs, but I would like to understand, whether an attempt has been made to understand how many cycles are possible apart from the 1-4-2-1 cycle in collatz problem
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Collatz sequences meet at a point

I was solving the problem,in which we are given two starting values of collatz sequence and our task is to say after how many steps their sequences “meet” for the first time. For ex - a= 7 , b= 8 a ...
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Is this a valid statement that would imply the Collatz Conjecture?

Let $f$ denote the Collatz transformation: $f(x) = \left\{ \begin{array}{ll} {x\over 2} & \quad x\equiv 0 \mod 2 \\ 3x+1 & \quad x \equiv 1\mod 2 ...
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1answer
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Simon Letherman, Dierk Schleicher, and Reg Wood 1999 paper on the 3n+1 problem, further results

I recently read with great interest the 1999 paper : "The 3n+1-Problem and Holomorphic Dynamics Simon Letherman, Dierk Schleicher, and Reg Wood" Experimental Mathematics 8: 3 (1999), 241–252. I ...
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How was the $3x+1$ problem checked up to $5 \times 2^{60}$?

The Wikipedia article for the Collatz conjecture states that: The conjecture has been checked by computer for all starting values up to $5 \times 2^{60} \approx 5.764 \times 10^{18}$. It gives ...
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133 views

arithmetic sequence $8n+1$ and the collatz conjecture

Is it a known result that if for all $n$ the collatz sequence of $8n+1$ lead to $1$, all natural numbers will?
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It's sufficient to prove collatz conjecture for $3+6k, k \geq 0$?

Thinking about this problem, I saw two interesting properties of Collatz graph. Firstly, if we consider that every even number $e$ can be represented (on a single way) as $e = o 2^n$, where $o$ is an ...
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For how many consecutive numbers Collatz conjecture was checked?

I heard here that Collatz conjecture was checked at least for every first $5 \cdot 10^{18}$ natural numbers, but I cannot find any source or actual information about this. Can anyone help to find out ...
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Examples of “eventually reaches y under iteration” other than the Collatz problem

The Collatz conjecture states that iteratively applying the map $$f(n) = \begin{cases} n/2 &\text{if } n \equiv 0 \pmod{2}\\ 3n+1 & \text{if } n\equiv 1 \pmod{2} .\end{cases}$$ to any ...
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1answer
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Repeating cycles in the $3n-1$ problem

While tracking sequences beginning with 1-to-3 digit integers, I have found 3 different repeating cycles in the $3n-1$ problem (similar to the Collatz Conjecture). They are 1, 2, 1..., 5, 14, 7, 20, ...
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Collatz cycle necessary condition.

Has it been established that a nontrivial m-cycle of the Collatz conjecture on the positive integers would require two consecutive raises (i.e., if $\{x_1, x_2, \ldots x_n\}$ is the odd positive ...