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A108146
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a(n)= 4*a(n-1) -a(n-2) -a(n-3).
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0
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1, 1, 1, 2, 6, 21, 76, 277, 1011, 3691, 13476, 49202, 179641, 655886, 2394701, 8743277, 31922521, 116552106, 425542626, 1553695877, 5672688776, 20711516601, 75619681751, 276094521627, 1008046888156, 3680473349246, 13437751987201
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OFFSET
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0,4
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LINKS
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Table of n, a(n) for n=0..26.
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FORMULA
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G.f.: (1-3*x-2*x^2)/(1-4*x+x^2+x^3). [Sep 28 2009]
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MATHEMATICA
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p = Expand[(x^3 - x^2 - x - 1)*(x^3 - 4*x^2 + x + 1)] v[0] = {1, 1, 1}; M = {{0, 1, 0}, {0, 0, 1}, {-1, -1, 4}}; Det[M - x*IdentityMatrix[3]] NSolve[Det[M - x*IdentityMatrix[3]] == 0, x] v[n_] := v[n] = M.v[n - 1] a = Table[v[n][[1]], {n, 0, 50}]
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CROSSREFS
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Sequence in context: A116819 A116782 A112091 * A116798 A116821 A116772
Adjacent sequences: A108143 A108144 A108145 * A108147 A108148 A108149
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KEYWORD
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nonn,easy
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AUTHOR
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Roger L. Bagula, Jun 05 2005
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EXTENSIONS
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Definition replaced by recurrence by the Associate Editors of the OEIS, Sep 28 2009
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STATUS
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approved
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