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 A026488 #22 Jul 22 2025 13:26:18 %S A026488 1,3,4,7,10,13,16,19,22,25,28,31,34,37,40,43,46,49,52,55,58,61,64,67, %T A026488 70,73,76,79,82,85,88,91,94,97,100,103,106,109,112,115,118,121,124, %U A026488 127,130,133,136,139,142,145,148,151,154,157,160,163,166,169,172 %N A026488 a(n) is the least positive integer > a(n-1) and not a(i)*a(j)-a(k) for 1 <= i <= j <= k <= n, where a(1) = 1. %C A026488 Conjecture: This is the increasing sequence of numbers congruent to 1 mod 3, with 3 inserted. %C A026488 Conjecture holds for n <= 1300. - _Sean A. Irvine_, Oct 12 2019 %Y A026488 Cf. A026477, A016777. %K A026488 nonn %O A026488 1,2 %A A026488 _Clark Kimberling_ %E A026488 Corrected and extended by _Clark Kimberling_, Oct 12 2019