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A123102
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a(0)=1, a(1)=0, a(2)=1, a(n) = a(n-1) + a(n-2) + 3*a(n-3).
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2
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1, 0, 1, 4, 5, 12, 29, 56, 121, 264, 553, 1180, 2525, 5364, 11429, 24368, 51889, 110544, 235537, 501748, 1068917, 2277276, 4851437, 10335464, 22018729, 46908504, 99933625, 212898316, 453557453, 966256644, 2058509045, 4385438048
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OFFSET
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0,4
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LINKS
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FORMULA
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G.f.: (1-x)/(1-x-x^2-3*x^3).
If p[1]=0, p[2]=1, p[i]=4, (i>2), and if A is Hessenberg matrix of order n defined by: A[i,j]=p[j-i+1], (i<=j), A[i,j]=-1, (i=j+1), and A[i,j]=0 otherwise, then, for n>=1, a(n)=det A. - Milan Janjic, May 02 2010
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MATHEMATICA
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LinearRecurrence[{1, 1, 3}, {1, 0, 1}, 40] (* Harvey P. Dale, May 04 2018 *)
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PROG
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(PARI) Vec((1-x)/(1-x-x^2-3*x^3) + O(x^40)) \\ Michel Marcus, Aug 07 2022
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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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