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 A053338 #7 Sep 15 2023 19:02:41
%S A053338 6,96,696,9696,69696,669696,6669696,96669696,696669696,9696669696,
%T A053338 69696669696,969696669696,9969696669696,69969696669696,
%U A053338 969969696669696,9969969696669696,99969969696669696,999969969696669696
%N A053338 a(n) contains n digits (either '6' or '9') and is divisible by 2^n.
%H A053338 Ray Chandler, <a href="/A053338/b053338.txt">Table of n, a(n) for n = 1..1000</a>
%F A053338 a(n)=a(n-1)+10^(n-1)*(6+3*[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 6, if not then n-th term begins with a 9.
%t A053338 Table[Select[FromDigits/@Tuples[{6,9},n],Mod[#,2^n]==0&],{n,20}]//Flatten (* _Harvey P. Dale_, Sep 15 2023 *)
%Y A053338 Cf. A023410, A050621, A050622, A035014.
%K A053338 base,nonn
%O A053338 1,1
%A A053338 _Henry Bottomley_, Mar 06 2000