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A236581
The number of tilings of a 7 X (4n) floor with 1 X 4 tetrominoes.
1
1, 5, 37, 269, 1949, 14121, 102313, 741305, 5371097, 38916077, 281964941, 2042966149, 14802232757, 107249008849, 777068573905, 5630220503025, 40793546383409, 295568073335893, 2141527121824885, 15516352499614333, 112423136012925517, 814557513519681785
OFFSET
0,2
COMMENTS
Tilings are counted irrespective of internal symmetry: Tilings that match each other after rotations and/or reflections are counted with their multiplicity.
FORMULA
G.f.: (1-x)^3/(-8*x+1+6*x^2-4*x^3+x^4).
MAPLE
g := (1-x)^3/(-8*x+1+6*x^2-4*x^3+x^4) ;
taylor(%, x=0, 30) ;
gfun[seriestolist](%) ;
MATHEMATICA
LinearRecurrence[{8, -6, 4, -1}, {1, 5, 37, 269}, 19] (* Jean-François Alcover, Feb 19 2019 *)
CROSSREFS
Cf. A003269 (4Xn floor), A236579 - A236582.
Sequence in context: A331449 A220634 A083232 * A262410 A089303 A164595
KEYWORD
nonn
AUTHOR
R. J. Mathar, Jan 29 2014
STATUS
approved