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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

REFERENCES

E. Deutsch, Counting tilings with L-tiles and squares, Problem 10877, Amer. Math. Monthly, 110 (March 2003), 245-246.

LINKS

Table of n, a(n) for n=0..28.

FORMULA

G.f.: (1-x-x^2)/(1-x-5*x^2-4*x^3+x^5).

CROSSREFS

Cf. A002478.

Sequence in context: A059480 A105723 A143555 * A075308 A020331 A248476

Adjacent sequences:  A025231 A025232 A025233 * A025235 A025236 A025237

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Mar 07 2003

STATUS

approved

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Last modified October 24 06:16 EDT 2014. Contains 248502 sequences.