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 A328581 #10 Mar 06 2024 01:01:26
%S A328581 1,1,1,1,2,2,1,1,1,1,2,2,2,2,2,2,4,4,3,3,3,3,6,6,4,4,4,4,8,8,1,1,1,1,
%T A328581 2,2,1,1,1,1,2,2,2,2,2,2,4,4,3,3,3,3,6,6,4,4,4,4,8,8,2,2,2,2,4,4,2,2,
%U A328581 2,2,4,4,4,4,4,4,8,8,6,6,6,6,12,12,8,8,8,8,16,16,3,3,3,3,6,6,3,3,3,3,6,6,6,6,6,6
%N A328581 Product of nonzero digits in primorial base expansion of n.
%C A328581 a(0) = 1 as an empty product.
%H A328581 Antti Karttunen, <a href="/A328581/b328581.txt">Table of n, a(n) for n = 0..32768</a>
%H A328581 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>.
%F A328581 a(n) = A005361(A276086(n)).
%t A328581 a[n_] := Module[{k = n, p = 2, s = 1, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, If[r > 0, s *= r]; p = NextPrime[p]]; s]; Array[a, 100, 0] (* _Amiram Eldar_, Mar 06 2024 *)
%o A328581 (PARI) A328581(n) = { my(m=1, p=2); while(n, if(n%p, m *= (n%p)); n = n\p; p = nextprime(1+p)); (m); };
%Y A328581 Cf. A005361, A049345, A276086, A324655, A328582.
%Y A328581 Cf. A276156 (positions of 1's).
%Y A328581 Cf. also A227153 (an analogous sequence).
%K A328581 nonn,base
%O A328581 0,5
%A A328581 _Antti Karttunen_, Oct 21 2019