I think I was trying to implement this solution, but missed some important steps and gave up:)

I know you want write a one-line solution, however it may cause you a lot of pain. Sometimes it is better to break problem into peaces and do tricks with the input.

I improved the assertion messages for Java so now this should be more clear.

Unfortuntelly, cannot pass tests ang get an error:
expected: java.util.Arrays$ArrayList<[]> but was: java.util.ArrayList<[]>

And this error is related to the last line in sample test using Stream.of()

Not a kata suggestion. See https://docs.codewars.com/training/troubleshooting/#post-discourse.

This kata requires a few lines of code to solve it, however it is not easy to complete if you are not familiar with RegEx.

Okay, I understand now. Thanks for responding and breaking it down. I really appreciate it.

Cheers.

I realize this comment was made 6 months ago, but your solution is the only one I can sort of understand (I'm not smart. It sucks).
Just had a question about this part: let start = 1 + seq_length * 2. Why do you multiply by two to get the values for start & end? Also, no worries if you don't want to answer.