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 A351567 #13 Mar 13 2024 01:51:06
%S A351567 0,0,0,1,0,2,0,1,1,1,1,2,0,2,2,1,2,2,0,3,3,1,3,2,0,4,4,1,4,2,0,1,1,1,
%T A351567 1,2,1,1,1,1,1,2,1,2,2,1,2,2,1,3,3,1,3,2,1,4,4,1,4,2,0,2,2,1,2,2,2,1,
%U A351567 1,1,1,2,2,2,2,1,2,2,2,3,3,1,3,2,2,4,4,1,4,2,0,3,3,1,3,2,3,1,1,1,1,2,3,2,2,1
%N A351567 The second least significant nonzero digit in the primorial base expansion of n, or 0 if there is no such digit.
%H A351567 Antti Karttunen, <a href="/A351567/b351567.txt">Table of n, a(n) for n = 0..60060</a>
%H A351567 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>.
%F A351567 a(n) = A351563(A276086(n)).
%F A351567 For all n, a(n) < A351566(n).
%t A351567 a[n_] := Module[{k = n, p = 2, s = {}, r}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, If[r > 0, AppendTo[s, r]]; p = NextPrime[p]]; i = Position[s, _?(# > 0 &)] // Flatten; If[Length[s] < 2, 0, s[[2]]]]; Array[a, 100, 0] (* _Amiram Eldar_, Mar 13 2024 *)
%o A351567 (PARI)
%o A351567 A351563(n) = if(1>=omega(n), 0, (factor(n))[2,2]);
%o A351567 A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
%o A351567 A351567(n) = A351563(A276086(n));
%Y A351567 Cf. A060735 (gives the positions of zeros after a(0)=0).
%Y A351567 Cf. A049345, A276086, A351563, A351566.
%K A351567 nonn,base
%O A351567 0,6
%A A351567 _Antti Karttunen_, Apr 01 2022