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 A381032 #8 Feb 17 2025 12:09:57
%S A381032 1,1,1,1,3,3,1,1,1,1,3,3,5,5,5,5,3,3,5,5,5,5,3,3,5,5,5,5,3,3,1,1,1,1,
%T A381032 3,3,1,1,1,1,3,3,5,5,5,5,3,3,5,5,5,5,3,3,5,5,5,5,3,3,7,7,7,7,3,3,7,7,
%U A381032 7,7,3,3,5,5,5,5,3,3,5,5,5,5,3,3,5,5,5,5,3,3,7,7,7,7,3,3,7,7,7,7,3,3,5,5,5,5,3,3,5
%N A381032 The radix prime of the least significant digit > 1 in the primorial base expansion of n, or 1 if there is no such digit.
%H A381032 Antti Karttunen, <a href="/A381032/b381032.txt">Table of n, a(n) for n = 0..65537</a>
%H A381032 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>.
%F A381032 a(n) = A008578(1+A328828(n)).
%F A381032 a(n) = A020639(A328572(n)) = A249739(A276086(n)).
%F A381032 For all n, a(n) divides A327860(n).
%o A381032 (PARI) A381032(n) = { my(p=2); while(n, if((n%p)>1, return(p)); n = n\p; p = nextprime(1+p)); (1); };
%Y A381032 Cf. A008578, A020639, A249739, A276086, A327860, A328572, A328828, A381033, A381034.
%Y A381032 Cf. A088860 (positions of records for values > 1), A276156 (positions of 1's).
%Y A381032 Cf. also A053669, A351566.
%K A381032 nonn
%O A381032 0,5
%A A381032 _Antti Karttunen_, Feb 13 2025