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 A026420 #12 Feb 08 2025 14:17:28
%S A026420 2,4,5,6,7,9,11,13,15,16,17,19,21,23,25,27,29,31,33,37,39,40,41,43,47,
%T A026420 48,49,51,53,56,57,59,61,67,69,70,71,72,73,79,81,83,87,88,89,93,97,
%U A026420 101,103,104,107,109,110,111,113,120,121,123,127
%N A026420 a(n) = least positive integer > a(n-1) and not a(i)*a(j) for 1<=i<j<=n, with initial terms 2,4.
%H A026420 Ivan Neretin, <a href="/A026420/b026420.txt">Table of n, a(n) for n = 1..1000</a>
%t A026420 a = {2, 4}; used = {a[[1]]*a[[2]]}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a]; AppendTo[a, k], {n, 3, 60}]; a (* _Ivan Neretin_, Mar 07 2016 *)
%Y A026420 Cf. A026416 and references therein.
%K A026420 nonn
%O A026420 1,1
%A A026420 _Clark Kimberling_
%E A026420 Name clarified by _Robert C. Lyons_, Feb 08 2025