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 A050076 #21 Oct 05 2019 11:26:51
%S A050076 1,2,4,8,16,5,10,3,6,12,24,48,96,32,64,21,7,14,28,9,18,36,72,144,288,
%T A050076 576,192,384,128,42,84,168,56,112,37,74,148,49,98,196,65,130,43,86,
%U A050076 172,57,19,38,76,25,50,100,33,11,22,44,88,29,58
%N A050076 a(n) = floor(a(n-1)/3) if this is not among 0, a(1), ..., a(n-2); otherwise a(n) = 2*a(n-1).
%C A050076 This permutation of the natural numbers is the "MD sequence" for (M,D) = (2,3). See A050000. - _Clark Kimberling_, Jun 30 2004
%H A050076 T. D. Noe, <a href="/A050076/b050076.txt">Table of n, a(n) for n = 1..10000</a>
%H A050076 Clark Kimberling, <a href="http://faculty.evansville.edu/ck6/integer/unsolved.html">Unsolved Problems and Rewards</a>.
%t A050076 Rest@Nest[Append[#, If[FreeQ[#, r = Quotient[#[[-1]], 3]], r, 2 #[[-1]]]] &, {0, 1}, 60] (* _Ivan Neretin_, Jul 31 2016 *)
%Y A050076 Cf. A050000 and references therein.
%K A050076 nonn
%O A050076 1,2
%A A050076 _Clark Kimberling_