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 A155543 #8 Jun 29 2023 12:36:37
%S A155543 2,4,16,64,256,1024,4096,16384,65536,262144,1048576,4194304,16777216,
%T A155543 67108864,268435456,1073741824,4294967296,17179869184,68719476736,
%U A155543 274877906944,1099511627776,4398046511104,17592186044416,70368744177664
%N A155543 a(n)=2*A081294(n).
%H A155543 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (4).
%F A155543 a(n)=A000302(n), n>0.
%F A155543 G.f.: 2*(1-2*x)/(1-4*x). [R. J. Mathar, Jul 23 2009]
%F A155543 Conjecture: a(n)=A090129(2n+2).
%t A155543 CoefficientList[Series[2(1-2x)/(1-4x),{x,0,30}],x] (* or *) Join[{2}, NestList[ 4#&,4,30]] (* _Harvey P. Dale_, Nov 13 2015 *)
%K A155543 nonn,easy
%O A155543 0,1
%A A155543 _Paul Curtz_, Jan 24 2009
%E A155543 Edited and extended by _R. J. Mathar_, Jul 23 2009