leftimage for poohprod.ru

Collatz Conjecture - an approach in Matlab

The Collatz conjecture (named after Lothar Collatz) is an unsolved conjecture in mathematics. This conjecture is also known as 3n + 1, Ulam’s, Kakutani’s problem, Thwaites’, Hasse's algorithm, or the Syracuse problem; the sequence of numbers involved is referred to as the hailstone sequence.

This is the sequence: take a positive integer n; if n is even, divide it by 2, and that's the next number in the sequence; if n is odd, the next number is 3n + 1 (this process has been called ‘Half or Triple Plus One’, or HPTPO). Repeat the process indefinitely... or until you reach 1.

Collatz conjecture flow

The conjecture is that no matter what number you start with, you will always eventually get to 1. So far, no one has found a case when this doesn’t happen, but the conjecture hasn’t been formally demonstrated.

A possible code in Matlab is as follows:

function [ns, seq] = collatz(n)
% Your first number in the sequence is n
seq(1) = n;
% You position an index on the next element of the sequence
i = 2;

% Repeat the iteration until you find a 1
while seq(i-1) ~= 1
% Use a modulus after division to find an even/odd number
if mod(seq(i-1), 2) == 0
% Step taken if even
seq(i) = seq(i-1)/2;
% Step taken if odd
seq(i) = 3*seq(i-1) + 1;
% Increment your index
i = i+1;
% Find the length of the sequence
ns = length(seq);

Now, let’s try our Collatz-sequence function from another script or from the command window. We start with 12 and want to know the sequence and the number of elements in that sequence.

clc; clear
[n, seq] = collatz(12)

and we get:

n = 10
seq = 12 6 3 10 5 16 8 4 2 1

Now, let’s say that we’d like to know what natural number up to 20 produces the longest sequence.

We can try something like this:

clc; clear
% We're going to start the sequences with integers up to 20
for i = 1 : 20
% We perform the function and get the number of elements
% in the sequence and the sequence itself
[n(i), seq{i}] = collatz(i);
% We find out what's the maximum number of steps found
[max_steps, ix] = max(n)
% We display the appropriate indexed sequence

And we get:

max_steps = 21
ix = 18
ans = 18 9 28 14 7 22 11 34 17
52 26 13 40 20 10 5 16 8
4 2 1

This means that if we start our sequence with 18, we get 21 elements in the sequence.

From 'Collatz Conjecture' to Matlab home

From 'Collatz Conjecture' to 'Flow Control Menu'


footer for collatz conjectrue page

Related pages

what does piecewise meandecimal to binary formulamodulus matlabrc circuits examplesascii table of alphabetsmatlab handlesmatlab solve linear equationformula for nominal interest ratematlab while loop exampleplotting a function in matlabeuclidean algorithm to find gcdintegral convergence calculatorcalculating a bell curvedefine salvage valuesolving systems of equations with matlabf distribution calculatorheaviside thetaascii value chartrc circuits problemshow to solve kvl and kcl problemsmatlab poisson distributionascii binary code tablewattage price calculatorscilab to matlab conversionapplications of smith chartgold band resistorsolve factorialstower of hanoi game solutionconditional statements matlabkvl and kcl solved problemsmatlab programming exampleshow to calculate scrap value of car11011 binarymatlab binomial coefficientbisection method matlab examplematlab axis squaremultiple regression matlabsqrt in matlabmatlab windowdefining function in matlabhow to sketch a piecewise functionmultiply matrix in matlabmaclaurin series cosxhalf life decay formulaconvert decimal to binary exampleradioactive decay formula calculatoronline ohms law calculatorcramers rule examplematlab chartsolve equation with matlabrc circuit differential equation solutionhalf life formula exponential decayascii table for special characterssimultaneous nonlinear equation solvermatlab string replacesurf matlab examplecalculate compound interest onlinesawtooth harmonicsinch to sq ft calculatorascii table printablebinary to decimal examplesmaclaurin series of sinxconversion from decimal to octalkcl electricalhow to do nonlinear regression in matlabformat hex matlabif statements in matlabpascal triangle formula calculatorauto scrap valueplot points in matlaboctal softwarefactorial multiplicationpolar graph matlabmaclaurin series cosh xoctal to binary tabletaylor expansion of sinxascii char mapconvert binary to grey codewhat is impulse functiononline definite integrationascii codes of alphabetspythagoras theorem solverdecimal to octal conversion examples