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A033121
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Base-3 digits are, in order, the first n terms of the periodic sequence with initial period 1,0,1.
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1
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1, 3, 10, 31, 93, 280, 841, 2523, 7570, 22711, 68133, 204400, 613201, 1839603, 5518810, 16556431, 49669293, 149007880, 447023641, 1341070923, 4023212770, 12069638311, 36208914933, 108626744800, 325880234401, 977640703203, 2932922109610, 8798766328831
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = 3*a(n-1) + a(n-3) - 3*a(n-4).
G.f.: x*(1+x^2) / ((1-x)*(1-3*x)*(1+x+x^2)). - Colin Barker, Dec 24 2015
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MATHEMATICA
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Table[FromDigits[PadRight[{}, n, {1, 0, 1}], 3], {n, 30}] (* or *) LinearRecurrence[ {3, 0, 1, -3}, {1, 3, 10, 31}, 30] (* Harvey P. Dale, Jan 20 2017 *)
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PROG
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(PARI) Vec(x*(1+x^2)/((1-x)*(1-3*x)*(1+x+x^2)) + O(x^30)) \\ Colin Barker, Dec 24 2015
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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