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 A084568 #18 May 09 2024 04:43:11
%S A084568 1,5,8,20,32,80,128,320,512,1280,2048,5120,8192,20480,32768,81920,
%T A084568 131072,327680,524288,1310720,2097152,5242880,8388608,20971520,
%U A084568 33554432,83886080,134217728,335544320,536870912,1342177280,2147483648
%N A084568 a(0)=1, a(1)=5, a(n+2)=4a(n), n>0.
%C A084568 Binomial transform is A080926 (without leading zero).
%H A084568 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,4)
%F A084568 G.f.: (1+5*x+4*x^2)/((1+2*x)*(1-2*x)).
%F A084568 E.g.f.: (9*exp(2*x)-exp(-2*x))/4-exp(0).
%F A084568 a(n) = (9*2^n-(-2)^n)/4-0^n.
%t A084568 Join[{1},LinearRecurrence[{0,4},{5,8},30]] (* _Harvey P. Dale_, Sep 12 2013 *)
%Y A084568 Cf. A080926, A104721.
%K A084568 nonn,easy
%O A084568 0,2
%A A084568 _Paul Barry_, May 30 2003