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 A026434 #15 Feb 06 2025 13:51:01
%S A026434 1,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,20,21,22,24,25,26,28,30,32,
%T A026434 33,36,37,38,40,42,45,46,48,50,52,56,57,58,60,61,66,68,70,72,73,75,78,
%U A026434 80,81,82,85,86,88,91,92,93,94,96,100
%N A026434 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n, with initial terms 1,4.
%H A026434 Ivan Neretin, <a href="/A026434/b026434.txt">Table of n, a(n) for n = 1..1000</a>
%t A026434 a = {1, 4}; 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 07 2016 *)
%Y A026434 Cf. A026431 and references therein.
%K A026434 nonn
%O A026434 1,2
%A A026434 _Clark Kimberling_
%E A026434 Name clarified by _Robert C. Lyons_, Feb 06 2025