

A239265


Number of domicule tilings of a 3 X 2n grid.


2



1, 5, 43, 451, 4945, 54685, 605707, 6710971, 74358721, 823915861, 9129240139, 101154812563, 1120826772817, 12419109262381, 137607593744107, 1524734943844939, 16894537473570817, 187196730554444581, 2074198005431257579, 22982759116542299875
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OFFSET

0,2


COMMENTS

A domicule is either a domino or it is formed by the union of two neighboring unit squares connected via their corners. In a tiling the connections of two domicules are allowed to cross each other.


LINKS



FORMULA

G.f.: (x^2+8*x1)/(3*x^3+21*x^213*x+1).


EXAMPLE

a(1) = 5:
++ ++ ++ ++ ++
o o o o oo oo oo
 X         
o o o o oo o o o o
         X 
oo oo oo o o o o
++ ++ ++ ++ ++.


MAPLE

gf:= (x^2+8*x1)/(3*x^3+21*x^213*x+1):
a:= n> coeff(series(gf, x, n+1), x, n):
seq(a(n), n=0..30);


CROSSREFS

Even bisection of column k=3 of A239264.


KEYWORD

nonn,easy


AUTHOR



STATUS

approved



