3x+1 with Lua with Explanation ~ Collatz Conjecture

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#1

3x+1, the simplest equation but unsolvable.

Today, we are going to be making a 3x+1 calculator by assuming x as a number.

If you don’t know what 3x+1 is, go check this video out.

Okay, first we going to say x is 8.

local x = 8
print(x)

Now, we have to make a while do statement if x is greater than 1

while x > 1 do

Firstly, we need to make an if statement.

if(x % 2) == 0 then

Now, we have to half x.

x = x / 2
print(x)

Lastly, we make an else statement.

else
x = x * 3 + 1
print(x)

Now, if you run it, the console will say 8, 4, 2, 1.
You can change local x = 8 to any number you want and it will end in a result of 1 no matter what.

If you want to watch my youtube video, I forgot two things in the video. On line 8, make a new line and type in print(n) . On line one, make a new line that says, print(n) . Sorry for the mistakes. (Just didn’t want to record it again)

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#2

The tutorial we didn’t know we needed. Thanks!

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#3

This is a very interesting topic. I made a Collatz Conjecture program in Lua a while back after being introduced to it by my maths teacher, although I extended it a fair bit more than this to actually search numbers and iterate through to try and find a number that didn’t end in the 4, 2, 1 loop. I started it from the highest number that had been previously checked (which is 295147905179352825856 from a quick google search). Never got a number that worked after leaving it to chug for about a week, but was interesting nonetheless. Here’s the code (for anyone interested :grin:). I didn’t use Roblox for this, which is why I don’t use table functions such as clear.

Code 
local testingNumber = 295147905179352825856
local workingNumber = 0
local workingTable = {}
local found = false

while true do
    for i, v in pairs(workingTable) do
        workingTable[i] = nil
    end
    if found == false then
        local foundLoop = false
        testingNumber = testingNumber + 1
        workingNumber = testingNumber
        print("testing " .. testingNumber)
        repeat
            table.insert(workingTable, workingNumber)
            if workingNumber % 2 == 0 then
                workingNumber = workingNumber / 2
            else
                workingNumber = (workingNumber * 3) + 1
            end
            for i, v in pairs(workingTable) do
                if v == workingNumber then
                    if v == 4 or v == 2 or v == 1 then
                        foundLoop = true
                    else
                        foundLoop = true
                        found = true
                        print(testingNumber .. " WORKS!!!!!!!!!!!!!!!!!")
                    end
                end
            end
        until foundLoop == true
    else
        print(testingNumber .. "WORKS!!!!!!!!!!!!!!!!!")
    end
end
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#4

Hey, I did some research on my own about this and made a 3x+1 calculator. Here’s the code:

local bestNum = 1

function calc(n, nFormed) -- 3x+1 calculation
    if n <= 1 then
        return nFormed
    end

    if n % 2 ~= 0 then
        n = (n * 3) + 1
    else
        n = n / 2
    end

    return calc(n, nFormed + 1)
end

for i = 1, 1000000000000 do
    local val = calc(i, 1)
    if val > bestNum then
        bestNum = val  -- save best result as highest val from calculation
        print(i, bestNum, "numbers formed")
    end
end

and here are the formatted data I collected over a long period of running this code:

number: 1 | formed 0 total numbers
number: 2 | formed 1 total numbers
number: 3 | formed 7 total numbers
number: 6 | formed 8 total numbers
number: 7 | formed 16 total numbers
number: 9 | formed 19 total numbers
number: 18 | formed 20 total numbers
number: 25 | formed 23 total numbers
number: 27 | formed 111 total numbers
number: 54 | formed 112 total numbers
number: 73 | formed 115 total numbers
number: 97 | formed 118 total numbers
number: 129 | formed 121 total numbers
number: 171 | formed 124 total numbers
number: 231 | formed 127 total numbers
number: 313 | formed 130 total numbers
number: 327 | formed 143 total numbers
number: 649 | formed 144 total numbers
number: 703 | formed 170 total numbers
number: 871 | formed 178 total numbers
number: 1,161 | formed 181 total numbers
number: 2,223 | formed 182 total numbers
number: 2,463 | formed 208 total numbers
number: 2,919 | formed 216 total numbers
number: 3,711 | formed 237 total numbers
number: 6,171 | formed 261 total numbers
number: 10,971 | formed 267 total numbers
number: 13,255 | formed 275 total numbers
number: 17,647 | formed 278 total numbers
number: 23,529 | formed 281 total numbers
number: 26,623 | formed 307 total numbers
number: 34,239 | formed 310 total numbers
number: 35,655 | formed 323 total numbers
number: 52,527 | formed 339 total numbers
number: 77,031 | formed 350 total numbers
number: 106,239 | formed 353 total numbers
number: 142,587 | formed 374 total numbers
number: 156,159 | formed 382 total numbers
number: 216,367 | formed 385 total numbers
number: 230,631 | formed 442 total numbers
number: 410,011 | formed 448 total numbers
number: 511,935 | formed 469 total numbers
number: 626,331 | formed 508 total numbers
number: 837,799 | formed 524 total numbers
number: 1,117,065 | formed 527 total numbers
number: 1,501,353 | formed 530 total numbers
number: 1,723,519 | formed 556 total numbers
number: 2,298,025 | formed 559 total numbers
number: 3,064,033 | formed 562 total numbers
number: 3,542,887 | formed 583 total numbers
number: 3,732,423 | formed 596 total numbers
number: 5,649,499 | formed 612 total numbers
number: 6,649,279 | formed 664 total numbers
number: 8,400,511 | formed 685 total numbers
number: 11,200,681 | formed 688 total numbers
number: 14,934,241 | formed 691 total numbers
number: 15,733,191 | formed 704 total numbers
number: 31,466,382 | formed 705 total numbers
number: 36,791,535 | formed 744 total numbers
number: 63,728,127 | formed 949 total numbers
number: 127,456,254 | formed 950 total numbers
-----------------------------------------------
lua + luajit results (quicker processing time)
-----------------------------------------------
number: 169,941,673 | formed 954 total numbers
number: 226,588,897 | formed 957 total numbers
number: 268,549,803 | formed 965 total numbers
number: 537,099,606 | formed 966 total numbers
number: 670,617,279 | formed 987 total numbers
number: 1,341,234,558 | formed 988 total numbers
number: 1,412,987,847 | formed 1001 total numbers
number: 1,674,652,263 | formed 1009 total numbers
number: 2,610,744,987 | formed 1051 total numbers
number: 4,578,853,915 | formed 1088 total numbers
number: 4,890,328,815 | formed 1132 total numbers

Edit: I do realise this is a year old post but its relevant and interesting - thanks for whoever reads this.

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