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A189003
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Number of domino tilings of the 5 X n grid with upper left corner removed iff n is odd.
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3
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1, 1, 8, 15, 95, 192, 1183, 2415, 14824, 30305, 185921, 380160, 2332097, 4768673, 29253160, 59817135, 366944287, 750331584, 4602858719, 9411975375, 57737128904, 118061508289, 724240365697, 1480934568960, 9084693297025, 18576479568193, 113956161827912
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OFFSET
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0,3
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LINKS
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FORMULA
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G.f.: (x-1)*(1+x)*(x^4+x^3-6*x^2+x+1) / (-x^8+15*x^6-32*x^4+15*x^2-1).
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MAPLE
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a:= n-> (<<0|1|0|0>, <0|0|1|0>, <0|0|0|1>, <-1|15|-32|15>>^iquo(n, 2, 'r').
`if`(r=0, <<8, 1, 1, 8>>, <<1, 0, 1, 15>>))[3, 1]:
seq(a(n), n=0..30);
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MATHEMATICA
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a[n_] := Product[2(2+Cos[2 j Pi/(n+1)]+Cos[k Pi/3]), {k, 1, 2}, {j, 1, n/2} ] // Round;
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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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STATUS
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approved
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