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 A373138 #15 Jul 15 2024 15:32:47
%S A373138 1,15,20,21,28,39,51,52,55,57,68,76,77,81,87,93,108,115,116,124,141,
%T A373138 143,144,161,183,185,187,188,192,201,205,209,215,219,225,237,244,256,
%U A373138 259,265,267,268,287,291,292,295,297,299,300,301,303,309,315,316,319,327,339,341,355,356,371,381,388,391,396,400,404
%N A373138 Numbers k such that A276085(k) is a multiple of 8, where A276085 is the primorial base log-function.
%C A373138 Because A276085 is completely additive, this is a multiplicative semigroup; if m and n are in the sequence then so is m*n.
%C A373138 The terms should be the integers in a multiplicative subgroup of the positive rationals. Denoting the k-th prime by p_k, a set of generators for this subgroup might be the union of {20, 81} with an infinite set constituted as follows: if p_k == 3 (mod 4) then p_k * p_{k+1} is in the set, if p_k == 1 (mod 4) then p_k^3 * p_{k+1} is in the set. - _Peter Munn_, Jul 15 2024
%H A373138 Antti Karttunen, <a href="/A373138/b373138.txt">Table of n, a(n) for n = 1..20000</a>
%H A373138 <a href="/index/Pri#primorial_numbers">Index entries for sequences related to primorial numbers</a>
%o A373138 (PARI) \\ See A373137.
%Y A373138 Cf. A002110, A276085, A373137 (characteristic function).
%Y A373138 Subsequence of A369002.
%Y A373138 Cf. A373259 (subsequence).
%K A373138 nonn
%O A373138 1,2
%A A373138 _Antti Karttunen_, May 26 2024