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A306944
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a(n) = number of iterations of x -> A306938(x) required to reach 1 when started at n, or -1 if the trajectory of n never reaches 1.
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5
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0, 2, 1, 4, -1, 3, 6, -1, 2, -1, -1, 5, -1, -1, -1, 4, -1, 4, -1, -1, 7, -1, -1, -1, -1, -1, 3, 6, -1, -1, -1, -1, -1, -1, -1, 6, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 5, 5, 8, -1, -1, -1, -1, 5, -1, -1, -1, -1, -1, -1, -1, -1, 8, -1, -1, -1, -1, -1, -1, -1
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OFFSET
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1,2
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COMMENTS
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If the trajectory of n contains two consecutive non-multiples of 3 then it increases for ever [te Riele].
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LINKS
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MATHEMATICA
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f[n_] := If[Divisible[n, 3], n/3, Floor[n*Sqrt[3]]]; a[n_] := Module[{k = n, inc = False, c = 0}, While[k > 1, kk = f[k]; If[inc && kk > k, c = -1; Break[]]; inc = kk > k; k = kk; c++]; c]; Array[a, 100]; (* Amiram Eldar, Mar 17 2019 *)
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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