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 A036215 #20 Jan 14 2024 08:05:58
%S A036215 1,3,9,27,69,207,621,3345,4275,25497,38247,229173,589185,1669443,
%T A036215 5205897,14045019,34319397,102566511,307313949,1843835217,2312645619,
%U A036215 13776780249,20417442711,112792132341,290155405761,847524815523,2611222884297,7627711248315
%N A036215 Binary reversal of 3^n.
%C A036215 Compute 3^n in binary, reverse the bits, from 0 to the most significant bit of the power.
%H A036215 Vincenzo Librandi, <a href="/A036215/b036215.txt">Table of n, a(n) for n = 0..1000</a>
%F A036215 a(n) = A030101(A000244(n)). - _Michel Marcus_, Sep 08 2013
%t A036215 Table[FromDigits[Reverse[IntegerDigits[3^n, 2]], 2], {n, 0, 30}] (* _Vincenzo Librandi_, Sep 09 2013 *)
%o A036215 (PARI) a(n) = subst(Polrev(binary(3^n)), x, 2); \\ _Michel Marcus_, Sep 08 2013
%Y A036215 Cf. A036213 and A036214.
%K A036215 nonn,base
%O A036215 0,2
%A A036215 _Antti Karttunen_
%E A036215 More terms from _Michel Marcus_, Sep 08 2013