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Search: id:A005424
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| A005424 |
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Related to iterates of bi-unitary totient function.
(Formerly M0530)
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+0
1
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| 2, 3, 4, 5, 8, 9, 13, 16, 17, 24, 25, 35, 44, 63, 64, 91, 97, 128, 193, 221, 259, 324, 353, 391, 477, 702, 929, 1188, 1269, 1589, 1613, 2017, 2309, 2623, 3397, 4064, 4781, 5468, 6515
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Let p(n) = number of unitary divisors k of n, k<n, which are relatively prime to n. Let p_1(n) = p(n), p_r(n) = p(p_{r-1}(n)). Sequence gives minimal r such that p_r(n)=1.
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REFERENCES
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M. Lal, H. Wareham and R. Mifflin, Iterates of the bi-unitary totient function, Utilitas Math., 10 (1976), 347-350.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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CROSSREFS
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Sequence in context: A161240 A165652 A063678 this_sequence A105317 A094103 A054181
Adjacent sequences: A005421 A005422 A005423 this_sequence A005425 A005426 A005427
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KEYWORD
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nonn,nice,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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