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 A325428 #7 Apr 30 2019 21:49:19
%S A325428 3,5,6,9,10,12,15,16,17,19,21,23,27,29,30,33,36,37,39,41,42,45,46,48,
%T A325428 49,51,52,53,57,60,63,64,65,66,69,70,71,75,77,81,82,84,87,88,89,91,93,
%U A325428 95,100,101,102,108,109,111,113,114,117,118,119,120,123,124
%N A325428 Complement of A325427.
%C A325428 These are the numbers 2x+1 and floor(3x/2) as x ranges through the numbers x>1 in A325427.
%H A325428 Clark Kimberling, <a href="/A325428/b325428.txt">Table of n, a(n) for n = 1..10000</a>
%t A325428 a = {1}; Do[AppendTo[a, NestWhile[# + 1 &, Last[a] + 1, Apply[Or,
%t A325428 Map[MemberQ[a, #] &, Select[Flatten[{(#-1)/2,
%t A325428 If[Mod[#, 3] == 0, (2 #)/3, 0] + If[Mod[#, 3] == 1, 1/3 (1 + 2 #), 0]}],
%t A325428 IntegerQ || # == 0]]] &]], {150}]; a (* A325427 *)
%t A325428 Complement[Range[Last[a]], a] (* A325428 *)
%t A325428 (* _Peter J. C. Moses_, Apr 25 2019 *)
%Y A325428 Cf. A325417, A325427.
%K A325428 nonn,easy
%O A325428 1,1
%A A325428 _Clark Kimberling_, Apr 30 2019