Prime Vowel Count - A Proposed New Problem

Dear Clive, thank you for the problem! I guess Mathias will say it's like 3 (at most) on his scale of difficulty of "CSF's problems" but I am trying it for the whole day already, in a number of attempts. I believe some of the previous puzzles give good hints (e.g. how to deal with range etc) and my solution seemingly is good for some cases, but still fails in others. Hopefully the idea is correct and I can finalize it with some debugging tomorrow :)

UPD: sure, approach was correct but obviously due to my passion to use weird languages I made a few silly mistake which affected calculations. Anyway the problem is amusing for involving several ideas and fusing them.

I indeed would give this a 3 on the CSF problem difficulty scale.

Thanks, Clive. This is a fun one.