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 A121537 #6 May 14 2025 10:43:12
%S A121537 1,5,6,7,8,9,11,13,17,19,23,25,29,30,31,35,37,40,41,42,43,45,47,48,49,
%T A121537 53,54,55,56,59,61,63,64,65,66,67,71,72,73,77,78,79,81,83,85,88,89,91,
%U A121537 95,97,99,101,102,103,104,107,109,113,114,115,117,119,121,125,127,131
%N A121537 If n appears then 2n, 3n and 4n do not.
%t A121537 s={1};Do[If[FreeQ[s,n/2]&&FreeQ[s,n/3]&&FreeQ[s,n/4],AppendTo[s,n]],{n,2,150}];s
%Y A121537 Cf. A003159 (if n appears then 2n does not), A036668 (if n appears then 2n and 3n do not).
%K A121537 nonn
%O A121537 1,2
%A A121537 _Zak Seidov_, Aug 06 2006