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 A022121 #68 Jun 27 2022 11:08:18
%S A022121 3,8,11,19,30,49,79,128,207,335,542,877,1419,2296,3715,6011,9726,
%T A022121 15737,25463,41200,66663,107863,174526,282389,456915,739304,1196219,
%U A022121 1935523,3131742,5067265,8199007,13266272,21465279,34731551,56196830,90928381,147125211
%N A022121 Fibonacci sequence beginning 3, 8.
%C A022121 From _Wajdi Maaloul_, Jun 20 2022: (Start)
%C A022121 a(n) is the number of ways to tile the figure below with squares and dominoes (a strip of length n+2 that contains two vertical strip of height 2 in its first and third tiles).
%C A022121 _ _
%C A022121 |_|_|_|_____ _
%C A022121 |_|_|_|_|_|_|...|_|
%C A022121 (End)
%H A022121 Vincenzo Librandi, <a href="/A022121/b022121.txt">Table of n, a(n) for n = 0..1000</a>
%H A022121 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a>
%H A022121 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,1).
%F A022121 G.f.: (3+5*x)/(1-x-x^2). - _Philippe Deléham_, Nov 19 2008
%F A022121 a(n) = F(n+2) + 2*L(n+1), where F(n) and L(n) are the n-th Fibonacci and Lucas number, respectively. - _Rigoberto Florez_, Jan 29 2020
%F A022121 E.g.f.: exp(-2*x/(1+sqrt(5)))*(-2*(5+6*sqrt(5))+(55+27*sqrt(5))*exp(sqrt(5)*x))/(5*(3+sqrt(5))). - _Stefano Spezia_, Jan 29 2020 after _Rigoberto Florez_
%F A022121 a(n) = Lucas(n+3) + Fibonacci(n-2). - _Greg Dresden_ and Steve Warren, Feb 28 2022
%t A022121 LinearRecurrence[{1, 1}, {3, 8}, 40] (* _Vladimir Joseph Stephan Orlovsky_, Sep 17 2008 *)
%t A022121 Table[2 LucasL[n+1] + Fibonacci[n+2], {n,0,40}] (* _Rigoberto Florez_, Jan 29 2020 *)
%o A022121 (Magma) a0:=3; a1:=8; [GeneralizedFibonacciNumber(a0, a1, n): n in [0..40]]; // _Vincenzo Librandi_, Jan 25 2017
%o A022121 (PARI) apply( {A022121(n)=[3,8]*([0,1;1,1]^n)[,1]}, [0..30]) \\ _M. F. Hasler_, Feb 28 2020
%Y A022121 Cf. A000032, A000045.
%K A022121 nonn,easy
%O A022121 0,1
%A A022121 _N. J. A. Sloane_