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 A140473 #7 Dec 17 2022 06:53:19
%S A140473 0,1,1,2,2,3,3,3,4,5,5,5,6,6,7,8,8,8,9,9,9,10,10,11,12,12,12,14,14,14,
%T A140473 14,14,15,15,15,16,18,18,18,18,18,20,21,21,21,22,22,22,23,23,23,23,23,
%U A140473 24,27,27,27,27,27,27,27,27,29,31,31,31,31,31,32,33,33,33,35,35,35,35
%N A140473 a(n) = a(floor(2*n/3)) + a(floor(n/3)), a(0) = 0, a(1) = 1.
%t A140473 a[0] = 0; a[1] = 1;
%t A140473 a[n_] := a[n] = a[Floor[2*n/3]] + a[Floor[n/3]];
%t A140473 Table[a[n], {n, 0, 200}]
%K A140473 nonn,easy
%O A140473 0,4
%A A140473 _Roger L. Bagula_ and _Gary W. Adamson_, Jun 28 2008