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A134438
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Number of tilings of a 3 X n rectangle with n trominoes.
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13
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1, 1, 3, 10, 23, 62, 170, 441, 1173, 3127, 8266, 21937, 58234, 154390, 409573, 1086567, 2882021, 7645046, 20279829, 53794224, 142696606, 378522507, 1004078871, 2663452699, 7065162260, 18741269167, 49713692146, 131872134232, 349808216915, 927912454723
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OFFSET
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0,3
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REFERENCES
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G. Kreweras, Recouvrements d'un rectangle de largeur 3 à l'aide de triminos, Mathématiques et sciences humaines, tome 130 (1995), p. 27-31.
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LINKS
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FORMULA
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a(n) = a(n-1) +2*a(n-2) +6*a(n-3) +a(n-4) -a(n-6).
G.f.: (1-x^3) / (1-x-2*x^2-6*x^3-x^4+x^6). - Alois P. Heinz, Oct 09 2008
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MAPLE
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a:= n-> (Matrix([[1$2, 0$2, 1, 0]]). Matrix(6, (i, j)-> if i+1=j then 1 elif j=1 then [1, 2, 6, 1, 0, -1][i] else 0 fi)^n)[1, 2]: seq(a(n), n=0..30); # Alois P. Heinz, Oct 09 2008
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MATHEMATICA
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LinearRecurrence[{1, 2, 6, 1, 0, -1}, {1, 1, 3, 10, 23, 62}, 40] (* Harvey P. Dale, Aug 27 2013 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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