@Deadcode I started chopping at your abundant regex, -22 so far

There are two spots where you do a multiplication when an addition would suffice. (Z - 1) / (\5 - 1) * \5 is better expressed as (Z - 1) + (Z - 1) / (\5 - 1). Same for \30. Those cost like 20 bytes each.

Down to 406. Here's the full history as a single pastebin: pastebin.com/raw/5jGjARc2

Latest version works in RegexMathEngine but not TIO, so one of those two is buggy :|

Bug report: (?=(x))?\1 matches 0 in ECMA but 1 in RME

Thankfully (?=pattern|) works in both at no cost in bytes

@Grimy Wow, that is absolutely magnificent! Would you like to post it as an answer? I'd like to give you some bounty for this.

@Grimy I'm aware of the bug. But that's the same as ()\1 isn't it? A lookahead will always trigger a no-match due to NEO+, so the (x) inside that lookahead will never be evaluated in any circumstance in ECMA.

If you've found a circumstance in which (?=anything)? will evaluate anything in proper ECMA then I definitely need to know.

Thanks!

I think you’re correct about that bug, I didn’t realize it was already known

I’m okay with posting mine as an answer, but it needs some more work first, if only for formatting/commenting

Okay awesome! :D

I currently have a 387 that only gets 64 wrong from 1-1000

I can’t prove it doesn’t have other false positives on prime powers, though

I've verified your 409 byte version up to 8000 so far

409 or 406?

Interesting that something gets only 64 wrong in 1-1000...

409

The pastebin I’ve posted has the 409 again instead of the 406

But the TIO link has the correct 406

Ohh

I took it from the pastebin

Where's the TIO link?

Comment on your answer

@Grimy :-O did you realize you commented "-98 bytes" exactly on this as well?

Yes x)

Though -98 out of 183 is a better ratio

:-O

Do you think amicable numbers might be possible? Domain ^x*,x*$

Or multiperfect numbers

Ooh amicable is an interesting challenge

Multi-perfect I think is possible with some virtualized math

@Grimy The 388 checks out up to 10000

Noice