

A025234


An Ltile 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 Ltiles.


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
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OFFSET

0,3


REFERENCES

E. Deutsch, Counting tilings with Ltiles and squares, Problem 10877, Amer. Math. Monthly, 110 (March 2003), 245246.


LINKS

Table of n, a(n) for n=0..28.
Index entries for linear recurrences with constant coefficients, signature (1,5,4,0,1).


FORMULA

G.f.: (1xx^2)/(1x5*x^24*x^3+x^5).


CROSSREFS

Cf. A002478.
Sequence in context: A059480 A105723 A143555 * A075308 A256456 A020331
Adjacent sequences: A025231 A025232 A025233 * A025235 A025236 A025237


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane, Mar 07 2003


STATUS

approved



