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A227200
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a(n) = a(n-1) + a(n-2) - 2^(n-1) with a(0)=a(2)=0, a(1)=-a(3)=1, a(4)=-5.
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2
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0, 1, 0, -1, -5, -14, -35, -81, -180, -389, -825, -1726, -3575, -7349, -15020, -30561, -61965, -125294, -252795, -509161, -1024100, -2057549, -4130225, -8284926, -16609455, -33282989, -66669660, -133507081, -267285605, -535010414, -1070731475
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OFFSET
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0,5
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LINKS
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FORMULA
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G.f.: x*(1-3*x)/((1-2*x)*(1-x-x^2)).
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MATHEMATICA
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Table[LucasL[n + 1] - 2^n, {n, 0, 30}] (* Bruno Berselli, Oct 03 2013 *)
CoefficientList[Series[x (1 - 3 x)/((1 - 2 x) (1 - x - x^2)), {x, 0, 40}], x](* Vincenzo Librandi, Oct 05 2013 *)
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PROG
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(BASIC)
LET N=0
LET L=0
LET M=1
PRINT L
PRINT M
FOR I=1 TO 30
LET N=M+L-(2)^(I-1)
PRINT N
LET L=M
LET M=N
NEXT I
END
(Magma) m:=30; R<x>:=PowerSeriesRing(Integers(), m); [0] cat Coefficients(R!((1-3*x)/((1-2*x)*(1-x-x^2)))); // Bruno Berselli, Oct 03 2013
(Magma) I:=[0, 1, 0, -1, -5]; [n le 5 select I[n] else Self(n-1)+Self(n-2)-2^(n-3): n in [1..35]]; // Vincenzo Librandi, Oct 05 2013
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CROSSREFS
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KEYWORD
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sign,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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