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 A118736 #10 Apr 14 2020 13:27:08
%S A118736 0,0,2,1,4,2,4,7,7,7,7,5,10,10,9,9,15,13,15,14,15,14,16,15,23,22,18,
%T A118736 13,20,21,23,24,25,19,25,24,31,25,25,30,36,26,29,30,36,38,28,37,36,45,
%U A118736 39,35,41,50,47,46,50,51,50,46,40,41,50,43,46,53,60,60,53,55,47,45,57,58
%N A118736 Number of zeros in binary expansion of 3^n.
%H A118736 Taylor Dupuy, David E. Weirich, <a href="https://doi.org/10.1016/j.jnt.2015.05.022">Bits of 3^n in binary, Wieferich primes and a conjecture of Erdős</a>, Journal of Number Theory, Volume 158, January 2016, Pages 268-280.
%t A118736 f[n_] := DigitCount[3^n, 2, 0]; Table[f[n], {n, 0, 73}] (* _Ray Chandler_, Sep 29 2006 *)
%o A118736 (PARI) a(n) = #select(x->(x==0), binary(3^n)); \\ _Michel Marcus_, Apr 14 2020
%Y A118736 Cf. A011754 (number of ones in binary expansion of 3^n).
%K A118736 base,nonn
%O A118736 0,3
%A A118736 _Zak Seidov_, May 22 2006