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 A178620 #5 Feb 06 2019 15:46:54
%S A178620 0,1,2,3,2,3,2,3,2,3,3,2,3,4,5,4,5,4,5,4,4,4,5,4,5,4,5,4,5,4,5,4,5,4,
%T A178620 5,4,5,6,7,3,3,4,5,5,4,5,4,5,4,5,5,6,7,4,4,5,5,5,4,5,5,4,5,6,7,5,7,6,
%U A178620 4,5,4,5,6,7,6,7,6,7,6,7,7,7,6,4,5,4,5,6,7,4,5,5,6,7,6,7,6,7,5,5,7,4,5,6,6
%N A178620 Sum of binary digits ( = sum of ternary digits ) of terms in A037301.
%H A178620 G. C. Greubel, <a href="/A178620/b178620.txt">Table of n, a(n) for n = 0..10000</a>
%t A178620 s = {}; Do[id3 = IntegerDigits[n, 3]; id2 = IntegerDigits[n, 2];
%t A178620 If[(t = Total[id2]) == Total[id3], AppendTo[s, t]], {n, 0, 10^3}]; s
%Y A178620 Cf. A037301 (sum of base 2 digits of n) = (sum of base 3 digits of n).
%K A178620 base,nonn
%O A178620 0,3
%A A178620 _Zak Seidov_, May 31 2010