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 A004662 #18 Sep 08 2022 08:44:33
%S A004662 1,3,11,33,121,363,1331,4213,14641,46343,163251,531773,2015761,
%T A004662 6051723,22175571,66571153,244153501,754502703,2705710511,10521531733,
%U A004662 31765015621,115737051263,351635174031
%N A004662 Powers of 3 written in base 8.
%H A004662 Vincenzo Librandi, <a href="/A004662/b004662.txt">Table of n, a(n) for n = 0..1000</a>
%t A004662 Table[FromDigits[IntegerDigits[3^n, 8]], {n, 0, 30}] (* _Vincenzo Librandi_, Jun 07 2013 *)
%o A004662 (PARI) vector(50, n, n--; fromdigits(digits(3^n, 8))) \\ _G. C. Greubel_, Oct 12 2018
%o A004662 (Magma) [Seqint(Intseq(3^n,8)): n in [0..50]]; // _G. C. Greubel_, Oct 12 2018
%Y A004662 Cf. A000244 (powers of 3), A007094 (numbers in base 8).
%K A004662 nonn,base,easy
%O A004662 0,2
%A A004662 _N. J. A. Sloane_