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A139763
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a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4) with a(n)=n+1 for n<=3.
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4
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1, 2, 3, 4, 11, 22, 43, 84, 171, 342, 683, 1364, 2731, 5462, 10923, 21844, 43691, 87382, 174763, 349524, 699051, 1398102, 2796203, 5592404, 11184811, 22369622
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n+1)-2a(n)=period 4:repeat 0, -1, -2, 3.
O.g.f.: (x-1)*(2*x^2+2*x+1)/((2*x-1)(1+x)(x^2+1)). a(n) = A056594(n+3)+((-1)^n+2^(n+1))/3. - R. J. Mathar, May 22 2008
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MATHEMATICA
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LinearRecurrence[{1, 1, 1, 2}, {1, 2, 3, 4}, 30] (* Harvey P. Dale, May 22 2021 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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