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URL: https://oeis.org/A239265

⇱ A239265 - OEIS

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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
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.
FORMULA
G.f.: -(x^2+8*x-1)/(3*x^3+21*x^2-13*x+1).
EXAMPLE
a(1) = 5:
+---+ +---+ +---+ +---+ +---+
|o o| |o o| |o-o| |o-o| |o-o|
| X | || || | | | | | |
|o o| |o o| |o-o| |o o| |o o|
| | | | | | || || | X |
|o-o| |o-o| |o-o| |o o| |o o|
+---+ +---+ +---+ +---+ +---+.
MAPLE
gf:= -(x^2+8*x-1)/(3*x^3+21*x^2-13*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.
Sequence in context: A385319 A112115 A350117 * A369023 A274666 A301976
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Mar 13 2014
STATUS
approved