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 A050084 #12 Oct 05 2019 11:31:53
%S A050084 1,5,25,8,2,10,3,15,75,375,125,41,13,4,20,6,30,150,50,16,80,26,130,43,
%T A050084 14,70,23,7,35,11,55,18,90,450,2250,750,250,83,27,9,45,225,1125,5625,
%U A050084 1875,625,208,69,345,115,38,12,60,300,100,33
%N A050084 a(n) = floor(a(n-1)/3) if this is not among 0, a(1), ..., a(n-2); otherwise a(n) = 5*a(n-1).
%H A050084 Ivan Neretin, <a href="/A050084/b050084.txt">Table of n, a(n) for n = 1..10000</a>
%t A050084 Rest@Nest[Append[#, If[FreeQ[#, r = Quotient[#[[-1]], 3]], r, 5 #[[-1]]]] &, {0, 1}, 55] (* _Ivan Neretin_, Jul 31 2016 *)
%Y A050084 Cf. A050000 and references therein.
%K A050084 nonn
%O A050084 1,2
%A A050084 _Clark Kimberling_