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A236583
The number of tilings of an 8 X (3n) floor with 2 X 3 hexominoes.
1
1, 1, 4, 11, 33, 96, 281, 821, 2400, 7015, 20505, 59936, 175193, 512089, 1496836, 4375251, 12788857, 37381824, 109267057, 319387565, 933569728, 2728823951, 7976351345, 23314871872, 68149361393
OFFSET
0,3
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)^2/(x^3-x^4+1-3*x).
MAPLE
g := (-1+x)^2/(x^3-x^4+1-3*x) ;
taylor(%, x=0, 30) ;
gfun[seriestolist](%) ;
CROSSREFS
Cf. A000079 (5 X n floor), A182097 (6 X n floor), A000244 (7 X n floor), A236584 (9 x 2n floor)
Sequence in context: A307073 A143787 A289973 * A025191 A282990 A099159
KEYWORD
easy,nonn
AUTHOR
R. J. Mathar, Jan 29 2014
STATUS
approved