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 A127867 Number of tilings of a 3xn board with 1x1 and L-shaped tiles (where the L-shaped tiles cover 3 squares). 8
 1, 1, 11, 39, 195, 849, 3895, 17511, 79339, 358397, 1620843, 7326991, 33127155, 149766353, 677103839, 3061202815, 13839823275, 62570318397, 282882722979, 1278922980071, 5782057329219, 26140890761969, 118183916056327, 534313772133687, 2415651952691819 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..500 P. Chinn, R. Grimaldi and S. Heubach, Tiling with L's and Squares, Journal of Integer Sequences, Vol. 10 (2007), Article 07.2.8 FORMULA G.f.: (1-x)^2/(1-3x-7x^2+x^3-2x^4). EXAMPLE a(2) = 11 because the 3x2 board can be tiled in one way with only square tiles, in 8 ways using one L-tile and 3 square tiles and in 2 ways with 2 L-tiles. MATHEMATICA Table[Coefficient[Normal[Series[(1 - x)^2/(1 - 3x - 7x^2 + x^3 - 2x^4), {x, 0, 30}]], x, n], {n, 0, 30}] CROSSREFS Cf. A127864, A127865, A127866, A127868, A127869, A127870. Column k=3 of A220054. - Alois P. Heinz, Dec 03 2012 Sequence in context: A004188 A163634 A173373 * A138050 A183940 A077568 Adjacent sequences:  A127864 A127865 A127866 * A127868 A127869 A127870 KEYWORD nonn AUTHOR Silvia Heubach (sheubac(AT)calstatela.edu), Feb 03 2007 STATUS approved

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Last modified October 21 08:47 EDT 2019. Contains 328292 sequences. (Running on oeis4.)