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 A325427 #7 Apr 30 2019 21:49:11
%S A325427 1,2,4,7,8,11,13,14,18,20,22,24,25,26,28,31,32,34,35,38,40,43,44,47,
%T A325427 50,54,55,56,58,59,61,62,67,68,72,73,74,76,78,79,80,83,85,86,90,92,94,
%U A325427 96,97,98,99,103,104,105,106,107,110,112,115,116,121,122,126
%N A325427 a(n) is the least number not 2*a(m)+1 or floor(3*a(m)/2) for any m < n.
%H A325427 Clark Kimberling, <a href="/A325427/b325427.txt">Table of n, a(n) for n = 1..10000</a>
%e A325427 The sequence necessarily starts with 1. The next 2 terms are determined as follows: because a(1) = 1, the number 3 is disallowed, so that a(2) = 2, whence the numbers 5 and 6 are disallowed, and a(3) = 4. See A325417 for a guide to related sequences.
%t A325427 a = {1}; Do[AppendTo[a, NestWhile[# + 1 &, Last[a] + 1, Apply[Or,
%t A325427 Map[MemberQ[a, #] &, Select[Flatten[{(#-1)/2,
%t A325427 If[Mod[#, 3] == 0, (2 #)/3, 0] + If[Mod[#, 3] == 1, 1/3 (1 + 2 #), 0]}],
%t A325427 IntegerQ || # == 0]]] &]], {150}]; a (* A325427 *)
%t A325427 Complement[Range[Last[a]], a] (* A325428 *)
%t A325427 (* _Peter J. C. Moses_, Apr 25 2019 *)
%Y A325427 Cf. A325417, A325428.
%K A325427 nonn,easy
%O A325427 1,2
%A A325427 _Clark Kimberling_, Apr 30 2019