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A003271
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Smallest number which requires n iterations of the unitary totient function (A047994) to reach 1.
(Formerly M0531)
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4
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1, 2, 3, 4, 5, 9, 16, 17, 41, 83, 113, 137, 257, 773, 977, 1657, 2048, 2313, 4001, 5725, 7129, 11117, 17279, 19897, 22409, 39283, 43657, 55457, 120677, 308941, 314521, 465089, 564353, 797931, 1110841, 1310443, 1924159, 2535041, 3637637, 6001937, 8319617, 9453569, 10969369
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| A049865(a(n)) = n and A049865(m) <> n for m < a(n). [Reinhard Zumkeller, Aug 17 2011]
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REFERENCES
| M. Lal, Iterates of the unitary totient function, Math. Comp., 28 (1974), 301-302.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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PROG
| (Haskell)
import Data.List (elemIndex)
import Data.Maybe (fromJust)
a003271 n = a003271_list !! n
a003271_list = map ((+ 1) . fromJust . (`elemIndex` a049865_list)) [0..]
-- Reinhard Zumkeller, Aug 17 2011
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CROSSREFS
| Cf. A047994.
Sequence in context: A060732 A068584 A107799 * A049796 A106165 A088817
Adjacent sequences: A003268 A003269 A003270 * A003272 A003273 A003274
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KEYWORD
| nonn,nice,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from David W. Wilson (davidwwilson(AT)comcast.net)
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