This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A328837 #15 Jan 02 2023 03:30:24
%S A328837 0,1,2,4,9,2312
%N A328837 Numbers k for which A328403(k) = A276086(A276086(A276086(k))) is squarefree.
%C A328837 Numbers k such that A276086(k) is in A328836, or equally, that A276087(k) is in A276156, i.e., numbers k for which A328828(A276087(k)) is zero, that is, numbers k such that in the primorial base expansion of A276087(k) there are no digits larger than 1.
%C A328837 All the terms of A328313 are also included in this sequence. Questions: Is that sequence finite? Even if it is, is this one also? Are there any terms here between 2312 and 3217644767340672907899084554132? Are there only finitely many numbers k for which A328828(A328403(k)) is zero? (See comments in A328398.)
%H A328837 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>
%o A328837 (PARI)
%o A328837 A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
%o A328837 A328828(n) = { my(i=1, p=2); while(n, if((n%p)>1, return(i)); i++; n = n\p; p = nextprime(1+p)); (0); };
%o A328837 isA328837(n) = !A328828(A276086(A276086(n)));
%Y A328837 Cf. A008966, A276086, A276087, A276156, A328313, A328403, A328828, A328836.
%Y A328837 Positions of ones in A328394. See also comments in A328398.
%K A328837 nonn,hard,more
%O A328837 1,3
%A A328837 _Antti Karttunen_, Oct 30 2019