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Search: id:A100411
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| A100411 |
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Numbers n such that n is the phi(n)-th nonprime number. |
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+0
2
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| 1, 4, 8, 27, 35, 215, 235, 2611, 65113, 174647, 1301317, 1302509, 5021647, 10885081, 36319939, 70112131, 70113559, 325575773
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OFFSET
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1,2
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COMMENT
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n is in the sequence iff n is't prime and n=phi(n)+pi(n). This sequence is a subsequence of A037170 and 2 is the only term of A037170 which isn't in this sequence because 2 is the only prime p such that p=phi(p)+pi(p).
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EXAMPLE
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27 is in the sequence because phi(27)=18 and 27 is the 18-th nonprime number, the first 17 nonprime numbers are 1,4,6,8,9,10,12,14,15,16,18,20,21,22,24,25 & 26.
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CROSSREFS
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Cf. A037170, A100410, A018252.
Adjacent sequences: A100408 A100409 A100410 this_sequence A100412 A100413 A100414
Sequence in context: A126733 A012982 A012952 this_sequence A065405 A026085 A036720
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KEYWORD
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more,nonn
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AUTHOR
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Farideh Firoozbakht (f.firoozbakht(AT)math.ui.ac.ir), Dec 01 2004
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