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A236580
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The number of tilings of a 6 X (4n) floor with 1 X 4 tetrominoes.
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2
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1, 4, 25, 154, 943, 5773, 35344, 216388, 1324801, 8110882, 49657576, 304020556, 1861317163, 11395616227, 69767835259, 427142397547, 2615110919020, 16010597772667, 98022320649478, 600125959188877, 3674175070596919, 22494548423870416, 137719270059617428
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OFFSET
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0,2
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COMMENTS
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Tilings are counted irrespective of internal symmetry: Tilings that match each other after rotations and/or reflections are counted with their multiplicity.
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LINKS
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FORMULA
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G.f.: (1-x)^3/(-7*x+1+6*x^2-4*x^3+x^4).
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MAPLE
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g := (1-x)^3/(-7*x+1+6*x^2-4*x^3+x^4) ;
taylor(%, x=0, 30) ;
gfun[seriestolist](%) ;
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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