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Search: id:A063507
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| A063507 |
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Least k such that k - phi(k) = n, or 0 if no such k exists. |
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+0
5
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| 2, 4, 9, 6, 25, 10, 15, 12, 21, 0, 35, 18, 33, 26, 39, 24, 65, 34, 51, 38, 45, 30, 95, 36, 69, 0, 63, 52, 161, 42, 87, 48, 93, 0, 75, 54, 217, 74, 99, 76, 185, 82, 123, 60, 117, 66, 215, 72, 141, 0, 235, 0, 329, 78, 159, 98, 105, 0, 371, 84, 177, 122, 135, 96, 305, 90, 427
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Inverse cototient (A051953) sets represented by their minimum, as in A002181 for totient function. Impossible values (A005278) are replaced by zero.
If a(n) > 0, then it appears that a(n) > 1.26n. - T. D. Noe
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
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FORMULA
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a(n)-A051953(a(n))=n if possible and a(n)=0 if n belongs to A005278.
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EXAMPLE
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x = InvCototient[24] = {36, 40, 44, 46}; Phi[x] = Phi[{36, 40, 44, 46}] = {12, 16, 20, 22}; x-Phi[x] = {24, 24, 24, 24}, so a(24) = Min[InvCototient[24]]; a(10) = 0 because 10 is in A005278.
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CROSSREFS
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Cf. A051953, A000010, A002181, A005277, A005278.
Cf. A063748 (greatest solution to x-phi(x)=n)
Sequence in context: A161360 A104654 A011182 this_sequence A055858 A141389 A133757
Adjacent sequences: A063504 A063505 A063506 this_sequence A063508 A063509 A063510
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Aug 09 2001
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Oct 25 2008 at the suggestion of R. J. Mathar.
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