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 A053334 #7 Aug 20 2025 17:32:58
%S A053334 6,16,616,1616,11616,111616,6111616,16111616,616111616,1616111616,
%T A053334 61616111616,661616111616,1661616111616,61661616111616,
%U A053334 661661616111616,6661661616111616,66661661616111616,666661661616111616
%N A053334 a(n) contains n digits (either '1' or '6') and is divisible by 2^n.
%H A053334 Ray Chandler, <a href="/A053334/b053334.txt">Table of n, a(n) for n = 1..1000</a>
%F A053334 a(n)=a(n-1)+10^(n-1)*(6-5*[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 1.
%t A053334 nxt[{n_,a_}]:={n+1,a+10^n (6-5*Mod[a/2^n,2])}; NestList[nxt,{1,6},20][[;;,2]] (* _Harvey P. Dale_, Aug 20 2025 *)
%Y A053334 Cf. A023406, A050621, A050622, A035014.
%K A053334 base,nonn
%O A053334 1,1
%A A053334 _Henry Bottomley_, Mar 06 2000