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 A094539 #12 Aug 26 2015 23:24:27
%S A094539 0,0,1,3,11,33,105,315,961,2883,8697,26091,78411,235233,706113,
%T A094539 2118339,6356243,19068729,57209865,171629595,514899771,1544699313,
%U A094539 4634130897,13902392691,41707276809,125121830427,375365787489,1126097362467
%N A094539 a(n) = A094538(n)/3.
%H A094539 Vincenzo Librandi, <a href="/A094539/b094539.txt">Table of n, a(n) for n = 0..1000</a>
%t A094539 a[0] = 1; a[n_] := a[n] = 3*a[n - 1] - If[EvenQ[n], a[n/2], 0]; Insert[Table[(3^(n) - a[n])/3, {n, 1, 30}], 0, 1] (* _Stefan Steinerberger_, Mar 24 2006 *)
%Y A094539 Cf. A003000, A019308, A094538.
%K A094539 nonn,easy
%O A094539 0,4
%A A094539 _N. J. A. Sloane_, Jun 06 2004
%E A094539 More terms from _Stefan Steinerberger_, Mar 24 2006