Problem 21. Return the 3n+1 sequence for n

Created by Cody Team

Solve Later

A Collatz sequence is the sequence where, for a given number n, the next number in the sequence is either n/2 if the number is even or 3n+1 if the number is odd. The sequence always terminates with 1.
So if
 n = 13
then
 c = [13    40    20    10     5    16     8     4     2     1]

Solve

Solution Stats

18499 Solutions
8400 Solvers

Last Solution submitted on Oct 21, 2025

Last 200 Solutions

Problem Comments

6 Comments

6 Comments

Show 3 older comments

Cedric on 5 Apr 2013

Hep, Cody Team, could you remove my solution please?

Cedric on 8 Apr 2013

Thank you!

Mandeep Singh on 14 Jun 2013

nice one but consumes size dunno how to reduce it

jubin soni on 13 Nov 2016

a bit tricky but nice

Dude on 17 Feb 2017

I like this problem, because I learnt about the Collatz sequence story. Very interessting.

Anant on 23 Mar 2024

function c = collatz(n)
c(1) = n;
while (1>0)
if (n == 1)
c(end+1) = n;
break
elseif (mod(n,2) == 0)
c(end+1) = n;
n = n/2;
collatz(n);
else
c(end+1) = n;
n = 3*n + 1;
collatz(n);
end
end
c(1) = [];
end

This solution is correct as I ran the Test Cases myself. But the compiler timed out. What should I do ?

Solution Comments

Show comments

Problem Recent Solvers8400

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 21. Return the 3n+1 sequence for n

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers8400

Suggested Problems

More from this Author96

Problem Tags

Community Treasure Hunt

Problem 21. Return the 3n+1 sequence for n

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers8400

Suggested Problems

More from this Author96

Problem Tags

Community Treasure Hunt

Players