Mapping the Collatz Conjecture in Excel

Hi guys, I was wondering if I could get some help as I'm not particularly proficient on Excel.

My excel problem is regarding a specific mathematical phenomenon called the 'Collatz Conjecture'

(For those who don't know the Collatz Conjecture, it is a mathematical problem where from whichever starting number you're at you multiply the number by 3 and add 1 if it's an odd number, if it is an even number you divide by 2. Eventually all of these sequences end up going back to the number 1.

There is a video by Veritasium on their youtube channel explaining the problem if you would prefer a fuller explanation, it is called: 'The Simplest Math Problem No One Can Solve - Collatz Conjecture')

I need to make a document which lists every number of the Collatz Conjecture sequence for the numbers between 1 - 131072.

With Row 1 being for the number 1, row 2 for number 2 etc...

Example (Row 3): Column A = 3, B = 10, C = 5, D = 16, E = 8, F = 4, G = 2, H = 1. We stop here as the sequence has reached 1.

However, the moment any sequence exceeds the number 131072, the cells in that row must be blank from that point on.

For example the sequence starting with 129,198 (which would be row 129,198):

A - 129,198
B - 64,599
C - 193,796 (at this point we have a value that exceeds 131,072 hence this cell should be empty)
D - empty cell
E - empty cell
F - empty cell
Etc...

I was hoping someone could guide me as to how to construct this excel spreadsheet, or if anyone has time on their hands and feels that it is a relatively simple exercise for them, to construct the spreadsheet for me and post it.

Apologies for the long text and thanks in advance

Welcome to the forum.

There are instructions at the top of the page explaining how to attach your sample workbook.

A good sample workbook has just 10-20 rows of representative data that has been desensitised. It also has expected results mocked up, worked examples where required, relevant cells highlighted and a few explanatory notes.

I'm not sure what part of programming this you are having trouble with. In Excel, it seems like it is mostly just a sequence of nested IF() functions that represents the desired logic. If you are unfamiliar with Excel's IF() function: https://support.microsoft.com/en-us/...c-aa8bbff73be2

1) Enter a starting value in A1.
2) In A2, build the desired nested IF() function:
2a) I start with the innermost test IF(ISEVEN(A1),A1/2,A1*3+1). If you are unfamiliar with the ISEVEN() function: https://support.microsoft.com/en-us/...4-2f479af55356 Also note that there is an ISODD() function if you would prefer to invert this IF() test.
2b) Nest that inside of an IF() test for previous value larger than max. IF(A1>131072,0,IF(ISEVEN(A1),...)). Note here that I chose 0 as the output rather than null string because 0 will propagate to the end without the need for another level of IF() testing. If you decide that it must output null string, then you can simply add another level of testing that propagates the null string to the bottom.
2c) Nest that inside of a test for the final 1 result =IF(A1=1,A1,IF(A1>131072,...))
3) Copy/paste/fill that formula down as far as needed for the longest expected sequence.

Mostly just a sequence of IF() functions. Any questions on how that goes into the spreadsheet?