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A127933
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Number of halving and tripling steps to reach 1 from the n-th pure hailstone number in the '3x+1' problem.
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2
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0, 0, 7, 8, 16, 19, 9, 17, 20, 20, 7, 10, 23, 111, 18, 26, 21, 21, 34, 8, 29, 16, 11, 24, 112, 112, 32, 19, 107, 27, 14, 22, 115, 14, 35, 35, 22, 9, 30, 17, 17, 12, 118, 25, 25, 38, 113, 113, 69, 33, 33, 20, 20, 46, 108, 46, 121, 28, 28, 41, 15, 15, 23, 116, 116
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OFFSET
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1,3
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COMMENTS
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Previous name was: A006577(k), k = pure hailstone numbers from A061641.
Impure hailstone numbers are those which occur in the trajectories of smaller numbers. Thus 5 is impure since it occurs in the trajectory of 3.
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LINKS
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FORMULA
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EXAMPLE
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3 is the 3rd term of A061641, the trajectory of 3 has 7 terms: (10, 5, 16, 8, 4, 2, 1), so a(3) = 7.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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Offset corrected and more terms added by Amiram Eldar, Feb 28 2020
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STATUS
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approved
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