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 A354131 #16 May 18 2022 13:13:17 %S A354131 1,2,12,48,216,936,4104,17928,78408,342792,1498824,6553224,28652616, %T A354131 125277192,547747272,2394904968,10471198536,45783025416,200176267464, %U A354131 875226954888,3826738469448,16731577137672,73155162229704,319854949515144,1398495821923656 %N A354131 Number of tilings of a 2 X n rectangle using 2 X 2 and 1 X 1 tiles, right trominoes and dominoes. %C A354131 Tiling algorithm see A351322. %H A354131 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,6). %F A354131 G.f.: (1 - x) / (1 - 3*x - 6*x^2). %F A354131 a(n) = 3*a(n-1) + 6*a(n-2). %e A354131 a(3)=48 %e A354131 Number of tilings without a 2 X 2 square: 44, see A353878. %e A354131 Number of other tilings: 4 %e A354131 ___ _ ___ _ _ ___ _ ___ %e A354131 | | | | |_| | | | |_| | %e A354131 |___|_| |___|_| |_|___| |_|___| %o A354131 (Maxima), see A352589. %Y A354131 Cf. A351322, A352589, A353878, A354130, A354132. %K A354131 nonn,easy %O A354131 0,2 %A A354131 _Gerhard Kirchner_, May 18 2022