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 A353964 #13 May 14 2022 22:37:13 %S A353964 1,1,6,13,45,122,373,1073,3182,9293,27349,80178,235509,691097,2028998, %T A353964 5955501,17482685,51318186,150642613,442198913,1298048350,3810328141, %U A353964 11184967717,32832705122,96378199989,282911661033,830468071222,2437782776365,7155946454541 %N A353964 Number of tilings of a 2 X n rectangle using 2 X 2 and 1 X 1 tiles and right trominoes. %C A353964 For tiling algorithm see A351322. %H A353964 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,5,2). %F A353964 G.f.: 1 / (1 - x - 5*x^2 - 2*x^3). %F A353964 a(n) = a(n-1) + 5*a(n-2) + 2*a(n-3). %e A353964 a(3)=13, see example 3 X 2, A353965. %o A353964 (Maxima) See A352589. %Y A353964 Cf. A351322, A352589, A353963, A353965. %K A353964 nonn,easy %O A353964 0,3 %A A353964 _Gerhard Kirchner_, May 13 2022