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A140888
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Number of nonprimes in [210n - 210, 210n] coprime to 210.
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0
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6, 13, 15, 16, 18, 19, 21, 17, 21, 21, 22, 23, 18, 22, 26, 21, 22, 21, 24, 24, 22, 25, 22, 22, 26, 24, 22, 21, 28, 23, 25, 23, 25, 24, 26, 25, 22, 27, 27, 24, 27, 22, 24, 25, 23, 26, 23, 28, 23, 26, 27, 26, 27, 26, 27, 30, 22, 26, 27, 22, 25, 24, 26, 29, 27, 24, 27, 31, 25, 26
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| For almost all n, a(n) = phi(210) = 48. It first attains this value at a(1751794).
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EXAMPLE
| {1,11,13,...,209,} are coprime to 210 in [0, 210]; the nonprimes are {1,121,143,169,187,209} so a(1) = 1.
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PROG
| (PARI) a(n)=sum(k=210*n-210, 210*n, gcd(k, 210)==1&!isprime(k))
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CROSSREFS
| Cf. A008364, A140887.
Sequence in context: A031113 A112610 A100205 * A053753 A090068 A070899
Adjacent sequences: A140885 A140886 A140887 * A140889 A140890 A140891
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KEYWORD
| nonn,easy,less
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AUTHOR
| Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jul 06 2008
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EXTENSIONS
| Corrected and rewritten by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Mar 26 2010
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