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 A108213 #20 Jun 15 2021 11:06:06
%S A108213 44,22,88,44,176,88,352,176,704,352,1408,704,2816,1408,5632,2816,
%T A108213 11264,5632,22528,11264,45056,22528,90112,45056,180224,90112,360448,
%U A108213 180224,720896,360448,1441792,720896,2883584,1441792,5767168,2883584,11534336,5767168
%N A108213 a(0)=44; if n odd, a(n) = a(n-1)/2, otherwise a(n) = 4*a(n-1).
%H A108213 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,2)
%F A108213 a(2n+1) = a(2n-2).
%F A108213 a(n) = 22 * 2^A028242(n). - _Franklin T. Adams-Watters_, Mar 29 2006
%F A108213 a(n) = 2a(n-2), a(0)=44, a(1)=22. G.f.: (44*x+88)/(1-2*x^2). - _Ralf Stephan_, Jul 16 2013
%t A108213 nxt[{n_,a_}]:={n+1,If[EvenQ[n],a/2,4a]}; Transpose[NestList[nxt,{0,44},40]] [[2]] (* or *) LinearRecurrence[{0,2},{44,22},40] (* _Harvey P. Dale_, Feb 21 2015 *)
%Y A108213 Twice A108732. Same as A108732 with first two terms deleted. - _Alexandre Wajnberg_, Dec 27 2005
%K A108213 nonn,easy
%O A108213 0,1
%A A108213 Guadalupe Garcia (lugar3628(AT)sbcglobal.net), Jun 15 2005
%E A108213 Explanation and more terms from _N. J. A. Sloane_, Aug 11 2005