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 A026431 #14 Feb 06 2025 13:50:50
%S A026431 1,2,3,4,6,8,9,10,12,13,14,16,18,20,21,22,24,28,30,32,33,34,36,37,40,
%T A026431 42,44,45,46,48,49,50,52,54,56,57,58,60,61,64,66,68,69,70,72,74,75,76,
%U A026431 78,80,81,82,84,85,86,88,90,92,93,94
%N A026431 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n, with initial terms 1,2.
%H A026431 Ivan Neretin, <a href="/A026431/b026431.txt">Table of n, a(n) for n = 1..1000</a>
%t A026431 a = {1, 2}; used = {a[[1]]*a[[2]] - 1}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a - 1]; AppendTo[a, k], {n, 3, 60}]; a (* _Ivan Neretin_, Mar 06 2016 *)
%Y A026431 Similar sequences with different starting conditions: A026432 (1,3), A026433 (2,3), A026434 (1,4), A026435 (2,4), A026436 (3,4).
%K A026431 nonn
%O A026431 1,2
%A A026431 _Clark Kimberling_
%E A026431 Name clarified by _Robert C. Lyons_, Feb 06 2025