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A102865
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Base-4 digits are, in order, the first n terms of the sequence (1, 3, 21, 203, 2021, 20203, 202021, 2020203, 20202021, 202020203, ... ).
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1
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1, 3, 9, 35, 137, 547, 2185, 8739, 34953, 139811, 559241, 2236963, 8947849, 35791395, 143165577, 572662307, 2290649225, 9162596899, 36650387593, 146601550371, 586406201481, 2345624805923, 9382499223689, 37529996894755, 150119987579017, 600479950316067
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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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4^n = a(n) + A037576(n) for n >= 1.
G.f.: 1 + x*(3-3*x-4*x^2)/((1-x)*(1+x)*(1-4*x)). - Colin Barker, Aug 28 2012
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MATHEMATICA
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FromDigits[IntegerDigits[#], 4]&/@(NestList[FromDigits[Flatten[ IntegerDigits[#]/.{3->{2, 1}, 1->{0, 3}}]]&, 1, 30]) (* or *) LinearRecurrence[{4, 1, -4}, {1, 3, 9}, 31](* Harvey P. Dale, Mar 23 2012 *)
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CROSSREFS
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KEYWORD
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base,easy,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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