Yes but the match goes for the first repetition the rest of the string isn’t matched no matter the length, again don’t find anything about prime numbers unless I checked something wrong. There is another guy who got it right it seems.

No cookie for me I just tried it in Notepad++ and VS code and it matches lines of one characer (first group I think) or the starting of a line that is an at least 2 characters string repeated twice (second group it seems)
so the second group matches abab
abcabc abcdeabce abcdefabcdef

Nothing about prime numbers really only first repetition gets a match. Very interesting Honestly I used regex from years and never had to retort to something like this ever. I can only imagine it useful to check for a password complexity to not be repeated strings like I do for sites that I just want in and use a yopmail.com mail to register a fake user.

IMO reddit has loads of bullshit bots and boosting but sadly it has some good targeted communities too.