⎕←{⍵⌷X[⍋X←∪∊*⌿¨1+⍳2⍴⍵]}20

@Sherlock9
225

Oh no wait that's just powers of powers

Okay so I just have to replace 1+⍳2⍴⍵ with a list of the first ⍵ primes joined with itself

*Cartesian product with itself, excuse me

Okay I have 24 bytes in Extended: tio.run/##SyzI0U2pTMzJT9dNrShJzUtJTfn/v/pR79ZHPdsjoh/…

Ah pardon me, I'm doing the prime powers of primes challenge codegolf.stackexchange.com/questions/144591/…

X[⍋←X] can be ⊢/⊂∘⍋

@Ven That doesn't appear to work

Oh I can remove the ∪ though. Remnant of earlier iterations

@Sherlock9 {⍵⌷∧∪∊∘.*⍨¯2⍭⍳⍵}

Not sure why *⍀ doesn't work instead of ∘.*

15 bytes! {⍵⌷∧∊∘.*⍨¯2⍭⍳⍵}

Ah, I found the issue with ⍀. Hard to fix though.

Best of luck fixing that then. I'm not sure I'll post this anyway since I'm fairly sure Extended post-dates that challenge by a significant margin

@Sherlock9 That's not an issue any more. Site policy now allows it.

@Adám Oh I hadn't realized we'd made a change. Alright, I'll post now and update the answer whenever a fix for ⍀ may come

@Sherlock9 It probably won't be fixed. The problem is that all the slashes are hybrid function/operator primitives, and there is no way for a user to define a hybrid. If I make the slashes operators, then A /⍨ B will mean B (A/) B and if I make them functions, then +/ B will mean + (/B). So I made them operators, but special-cases (with regex!) A /⍨ B to mean A {⍺ Slash ⍵}⍨ B but now we actually want ∊ *⍀⍨ B to mean ∊ B *BackslashBar B and not ∊ * B {⍺ BackslashBar ⍵}⍨ B

Oh geez

@Sherlock9 Don't forget to request a bounty!

Ooh let me dig through my APL answers over the past month

@Adám I've requested 4 bounties!

@Sherlock9 Good, good. I have more rep than I can use. Unfortunately, I can only have 3 active bounties at a time, but I will get around to yours.

Thanks muchly in advance

I need to edit that bounty list too ;P