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 A226322 Number of tilings of a 4 X n rectangle using L tetrominoes and 2 X 2 tiles. 10
 1, 0, 3, 6, 19, 48, 141, 378, 1063, 2920, 8115, 22418, 62123, 171876, 475919, 1317250, 3646681, 10094356, 27943739, 77353070, 214129845, 592752572, 1640859689, 4542223926, 12573787053, 34806745800, 96352029241, 266721635838, 738338745535, 2043868995512 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (0,5,6,4,0,-1,0,-3,-2,-4,0,-2). FORMULA G.f.: (x^6+2*x^2-1) / (-2*x^12 -4*x^10 -2*x^9 -3*x^8 -x^6 +4*x^4 +6*x^3 +5*x^2-1). EXAMPLE a(3) = 6: ._____.  ._____.  .___._.  ._.___.  ._____.  ._____. | .___|  |___. |  |   | |  | |   |  |___. |  | .___| |_|_. |  | ._|_|  |___| |  | |___|  |   |_|  |_|   | |   | |  | |   |  | |___|  |___| |  |___| |  | |___| |___|_|  |_|___|  |_____|  |_____|  |_____|  |_____| MAPLE a:= n-> (Matrix(12, (i, j)-> `if`(i+1=j, 1, `if`(i=12,     [-2, 0, -4, -2, -3, 0, -1, 0, 4, 6, 5, 0][j], 0)))^(n+8).     <<-1, 0, 1/2, [0\$5][], 1, 0, 3, 6>>)[1, 1]: seq(a(n), n=0..40); MATHEMATICA a[n_] := MatrixPower[ Table[ If[i+1 == j, 1, If[i == 12, {-2, 0, -4, -2, -3, 0, -1, 0, 4, 6, 5, 0}[[j]], 0]], {i, 1, 12}, {j, 1, 12}], n+8].{-1, 0, 1/2, 0, 0, 0, 0, 0, 1, 0, 3, 6} // First; Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Dec 05 2013, after Maple *) CROSSREFS Cf. A054854, A054856, A084480, A165716, A165791, A165799, A174248, A232497, A233191, A233266. Sequence in context: A219286 A104264 A007098 * A148566 A148567 A148568 Adjacent sequences:  A226319 A226320 A226321 * A226323 A226324 A226325 KEYWORD nonn,easy AUTHOR Alois P. Heinz, Jun 03 2013 STATUS approved

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Last modified January 27 23:41 EST 2022. Contains 350654 sequences. (Running on oeis4.)