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 A025234 An L-tile is a 2 X 2 square with the upper 1 X 1 subsquare removed; no rotations are allowed. a(n) = number of tilings of a 4 X n rectangle using tiles that are either 1 X 1 squares or L-tiles. 1
 1, 0, 4, 8, 28, 83, 255, 778, 2377, 7259, 22173, 67721, 206844, 631764, 1929609, 5893632, 18001012, 54980764, 167928588, 512906847, 1566579211, 4784826786, 14614369465, 44636891651, 136335139273, 416410496177, 1271848932360, 3884627600872, 11864877355729 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS E. Deutsch, Counting tilings with L-tiles and squares, Problem 10877, Amer. Math. Monthly, 110 (March 2003), 245-246. Index entries for linear recurrences with constant coefficients, signature (1,5,4,0,-1). FORMULA G.f.: (1-x-x^2)/(1-x-5*x^2-4*x^3+x^5). CROSSREFS Cf. A002478. Sequence in context: A105723 A280118 A143555 * A075308 A300461 A280085 Adjacent sequences:  A025231 A025232 A025233 * A025235 A025236 A025237 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Mar 07 2003 STATUS approved

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Last modified August 4 08:25 EDT 2020. Contains 336201 sequences. (Running on oeis4.)