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A306971
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The number of initial values <= 10^n whose trajectory under the iteration x -> A306938(x) reaches 1.
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0
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OFFSET
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1,1
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COMMENTS
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te Riele noted that of the first initial values <= 10^5 only 459 have a trajectory that reaches 1 and conjectured that almost all trajectories tend to infinity.
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LINKS
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EXAMPLE
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a(1) = 7 since 7 of the initial values 1 to 10 (all except 5, 8, and 10) have a trajectory that reaches 1 (their A306944 value is not -1).
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MATHEMATICA
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f[n_] := If[Divisible[n, 3], n/3, Floor[n*Sqrt[3]]]; itnum[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]; p=10; s={}; c=0; Do[i=itnum[n]; If[i>-1, c++]; If[n==p, AppendTo[s, c]; p*=10], {n, 1, 10000}]; s
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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