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 A328828 #14 Feb 23 2025 09:27:10
%S A328828 0,0,0,0,2,2,0,0,0,0,2,2,3,3,3,3,2,2,3,3,3,3,2,2,3,3,3,3,2,2,0,0,0,0,
%T A328828 2,2,0,0,0,0,2,2,3,3,3,3,2,2,3,3,3,3,2,2,3,3,3,3,2,2,4,4,4,4,2,2,4,4,
%U A328828 4,4,2,2,3,3,3,3,2,2,3,3,3,3,2,2,3,3,3,3,2,2,4,4,4,4,2,2,4,4,4,4,2,2,3,3,3,3
%N A328828 Index of the least significant digit larger than one in the primorial base expansion of n, 0 if no such digit exists.
%H A328828 Antti Karttunen, <a href="/A328828/b328828.txt">Table of n, a(n) for n = 0..65537</a>
%H A328828 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>.
%F A328828 a(n) = A277885(A276086(n)) = A055396(A328572(n)).
%F A328828 a(n) = A000720(A381032(n)). - _Antti Karttunen_, Feb 23 2025
%t A328828 a[n_] := Module[{k = n, p = 2, s = {}, r, i}, While[{k, r} = QuotientRemainder[k, p]; k != 0 || r != 0, AppendTo[s, r]; p = NextPrime[p]]; i = FirstPosition[s, _?(# > 1 &)]; If[MissingQ[i], 0, i[[1]]]]; Array[a, 100] (* _Amiram Eldar_, Mar 13 2024 *)
%o A328828 (PARI) A328828(n) = { my(i=1, p=2); while(n, if((n%p)>1, return(i)); i++; n = n\p; p = nextprime(1+p)); (0); };
%Y A328828 Cf. A000720, A049345, A055396, A276086, A276156 (positions of 0's), A277885, A328572, A328829 [= a(A276086(n))], A328832, A381032 [= A008578(1+a(n))].
%K A328828 nonn,base
%O A328828 0,5
%A A328828 _Antti Karttunen_, Oct 29 2019