(In reply to
re: Analytic attempt...? by Steve Herman)
Great catch, can't believe I didn't think of checking mod 9 after checking mod 3. That's what I get for solving before coffee in the morning.
I think n could be 8 mod 9 though, since n^2 would be 1 mod 9 and n^3 would be 8 mod 9, so the sum of all their digits would also be 0 mod 9.
Edited on April 7, 2021, 2:28 pm

Posted by tomarken
on 20210407 14:28:14 