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A050112
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a(n) = floor(a(n-1)/4) if this is positive and not yet in the sequence, otherwise a(n) = 6*a(n-1).
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5
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1, 6, 36, 9, 2, 12, 3, 18, 4, 24, 144, 864, 216, 54, 13, 78, 19, 114, 28, 7, 42, 10, 60, 15, 90, 22, 5, 30, 180, 45, 11, 66, 16, 96, 576, 3456, 20736, 5184, 1296, 324, 81, 20, 120, 720, 4320, 1080, 270, 67, 402, 100, 25, 150, 37, 222, 55
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Rest@Nest[Append[#, If[FreeQ[#, r = Quotient[#[[-1]], 4]], r, 6 #[[-1]]]] &, {0, 1}, 54] (* Ivan Neretin, Jul 31 2016 *)
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PROG
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(PARI) first(n)=my(v=vector(n), t); v[1]=1; for(i=2, n, t=v[i-1]\4; if(t<2, v[i]=6*v[i-1]; next); for(j=1, i-1, if(v[j]==t, v[i]=6*v[i-1]; next(2))); v[i]=t); v \\ Charles R Greathouse IV, Jul 31 2016
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CROSSREFS
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Cf. A050000 and references therein.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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