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Search: id:A063830
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| A063830 |
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a(n+1) is the smallest odd m such that its cototient equals a(n). |
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+0
1
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| 1, 3, 9, 21, 45, 117, 297, 585, 1521, 3105, 6993, 14553, 43653, 90885, 185925, 397125, 847125, 1813125, 3238725, 7556829, 17253789, 36910365, 94571997, 220301277, 475043037
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OFFSET
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1,2
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FORMULA
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a(n)=Min{x, odd : A051953[ a(n-1) ]=a(n)}; a(1)=1; a(2)=3, least odd prime; a(n)=Min[ Select[ Range[ a, b ], Equal[ #-EulerPhi[ # ], a(n-1) ]& ] ]
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EXAMPLE
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a(5)=45, cototient(45)=45-Phi(45)=45-24=21=a(4). This iteration with even numbers might stop, like {1,2,4,6,10} does if the last computed number has no InvCot, like 10 which is a non-cototient number.
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CROSSREFS
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A051953, A005278.
Sequence in context: A107351 A068156 A052101 this_sequence A062444 A141156 A014286
Adjacent sequences: A063827 A063828 A063829 this_sequence A063831 A063832 A063833
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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 21 2001
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jul 23 2002
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