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A222292
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Least number whose Collatz 3x+1 trajectory contains a number >= 2^n.
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3
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1, 3, 3, 3, 3, 7, 15, 15, 27, 27, 27, 27, 27, 27, 447, 447, 703, 703, 1819, 1819, 1819, 4255, 4255, 9663, 9663, 20895, 26623, 60975, 60975, 60975, 77671, 113383, 159487, 159487, 159487, 665215, 1042431, 1212415, 2684647, 3041127, 4637979, 5656191, 6416623
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OFFSET
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0,2
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COMMENTS
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This sequence is important for the computation of Collatz numbers. It shows that using 31-bit integers, only numbers less than 159487 can have their Collatz trajectory computed.
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LINKS
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MATHEMATICA
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mcoll[n_]:=Max@@NestWhileList[If[EvenQ[#], #/2, 3#+1] &, n, #>1 &]; i=1; Join[{1, 3}, Table[i=i; While[mcoll[i]<2^n, i=i+2]; i, {n, 2, 30}]] (* Jayanta Basu, May 27 2013 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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