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 A004646 #17 Sep 08 2022 08:44:33
%S A004646 1,2,4,11,22,44,121,242,514,1331,2662,5654,14641,32612,65524,164351,
%T A004646 362032,1054064,2141161,4312352,11625034,23553101,50436202,131205404,
%U A004646 262414111,555131222,1443262444,3216555221,6436443442,16206220214,35415440431,104134211162
%N A004646 Powers of 2 written in base 7.
%H A004646 Vincenzo Librandi, <a href="/A004646/b004646.txt">Table of n, a(n) for n = 0..1000</a>
%t A004646 Table[FromDigits[IntegerDigits[2^n, 7]], {n, 0, 40}] (* _Vladimir Joseph Stephan Orlovsky_, Feb 17 2012 *)
%o A004646 (PARI) for(n=0,30, print1(fromdigits(digits(2^n, 7)), ", ")) \\ _G. C. Greubel_, Sep 10 2018
%o A004646 (Magma) [Seqint(Intseq(2^n, 7)): n in [0..30]]; // _G. C. Greubel_, Sep 10 2018
%K A004646 nonn,base,easy
%O A004646 0,2
%A A004646 _N. J. A. Sloane_