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 A277734 #14 Mar 20 2023 06:42:43
%S A277734 5,10,16,21,29,34,40,45,53,58,63,69,74,82,87,93,98,106,111,116,122,
%T A277734 127,133,138,146,151,157,162,170,175,180,186,191,199,204,210,215,223,
%U A277734 228,233,239,244,250,255,263,268,274,279,287,292,298,303,311,316,321,327,332,340,345,351,356,364,369,374
%N A277734 Positions of 2's in A277731.
%C A277734 {A277732, A277733, A277734} forms a three-way partition of the positive integers, similar to {A003144, A003145, A003146}.
%H A277734 N. J. A. Sloane, <a href="/A277734/b277734.txt">Table of n, a(n) for n = 1..10000</a>
%p A277734 See A277732.
%t A277734 m = 1000; (* number of terms of A277731 *)
%t A277734 S[1] = {0};
%t A277734 S[n_] := S[n] = SubstitutionSystem[{0 -> {0, 1}, 1 -> {0, 1, 2}, 2 -> {0}}, S[n - 1]];
%t A277734 For[n = 2, True, n++, If[PadRight[S[n], m] == PadRight[S[n - 1], m], Print["n = ", n]; Break[]]];
%t A277734 A277731 = Take[S[n], m];
%t A277734 Position[A277731, 2] // Flatten (* _Jean-François Alcover_, Mar 20 2023 *)
%Y A277734 Cf. A052980, A277731, A277732, A277733.
%Y A277734 Cf. also A003144, A003145, A003146.
%K A277734 nonn
%O A277734 1,1
%A A277734 _N. J. A. Sloane_, Nov 07 2016