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 A179526 #4 May 30 2021 14:15:44
%S A179526 1,4,4,4,13,13,13,13,13,13,13,13,13,40,40,40,40,40,40,40,40,40,40,40,
%T A179526 40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,40,121,121,121,121,121,
%U A179526 121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121,121
%N A179526 (3^k - 1)/2 appears 3^(k-1) times, k>0.
%F A179526 a(n+1) = 3*a(floor(n/3)) + 1; a(0) = 1.
%t A179526 Table[PadRight[{},3^(k-1),(3^k-1)/2],{k,5}]//Flatten (* _Harvey P. Dale_, May 30 2021 *)
%Y A179526 Cf. A003462, A007448, A003817.
%K A179526 nonn
%O A179526 0,2
%A A179526 _Reinhard Zumkeller_, Jul 18 2010
%E A179526 Erroneous comment deleted by _Reinhard Zumkeller_, Jul 23 2010