I've had this puzzle on my phone for years. Every few months I'd glance at it and try and solve it. Last night, as I was eating dinner, I finally figured out the answer!

https://sh.itjust.works/post/55641581

Hah, took me nearly a minute.

Tap for spoiler

Add the digits on both sides. ? = 12

But I only got it so quickly because I enjoyed a similar puzzle once.

1
11
21
1211
111221
312211

continue the series.

Did I get it?

answer

13112221

Yes, that’s the solution
Keep going until you reach a 4!
Thanks for the hint. I kept on overthinking it.
Please explain more
Is this an honest question for information or a sarcastic slap on the wrist because my puzzle is basically a hint for OPs?
No I’m dumb but eventually figured it out after reading literally every comment in the thread. This one genuinely made me feel stupid.

Whaaat?

Isn’t it right parent minus left parent equals the node you pick?

Alternately right parent minus child equals left parent.

Why does it work with digits as well? What math sorcery is this??

21 minus 13 is unfortunately not 7… Unless I’ve misunderstood what you mean?

312211

13112221
1113213211
31131211131221

Wonder if/when a 4 would ever show up… and what the formula for that would look like

Your mother’s a 4.
And your father smelt of elderberries! Harumphh

Yeah. Probably.

You realize a 4 never will happen, right?

Not with that attitude, it won’t

Edit: I found the nerdy stuff I was curious about

Edit edit: and the real good stuff

A005150 - OEIS

Think about it.

To get a 4, you need either 1111, which can’t happen because thats just 21, or you have 211112, which would again just be 31.

Seems you can’t have a series that ends in anything but 1, if it starts from 1?

2
12
1112
3112
132112
1113122112
311311222112
13211321322112
1113122113121113222112

I wonder if this type of series would eventually become repeating… or is it irrational?

Still curious what the mathematical proof would look like. Not that I’d be able to understand it regardless, but curious nonetheless

You have the wrong answer in your spoiler. That answer is even (indirectly) called out in the description of the puzzle.