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 A026439 #18 Feb 06 2025 13:51:24
%S A026439 2,3,4,6,9,10,12,13,14,16,18,20,21,22,24,28,30,32,33,34,36,37,40,42,
%T A026439 44,45,46,48,49,50,52,54,56,57,58,60,61,64,66,68,69,70,72,74,75,76,78,
%U A026439 81,82,84,85,86,88,90,92,93,94,96,100,102
%N A026439 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2, with initial terms 2,3.
%H A026439 Ivan Neretin, <a href="/A026439/b026439.txt">Table of n, a(n) for n = 1..1000</a>
%t A026439 a = {2, 3}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* _Ivan Neretin_, Feb 15 2018 *)
%Y A026439 Cf. A026437 and references therein.
%K A026439 nonn
%O A026439 1,1
%A A026439 _Clark Kimberling_
%E A026439 Name clarified by _Robert C. Lyons_, Feb 06 2025