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A036997
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Number of composite numbers <= n and relatively prime to n.
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7
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0, 0, 0, 0, 1, 0, 2, 0, 2, 1, 5, 0, 6, 1, 3, 2, 9, 0, 10, 1, 5, 3, 13, 0, 11, 4, 9, 4, 18, 0, 19, 5, 10, 6, 14, 2, 24, 7, 13, 5, 27, 1, 28, 7, 11, 9, 31, 2, 27, 6, 18, 10, 36, 3, 25, 9, 21, 13, 41, 1, 42, 13, 19, 14, 31, 4, 47, 14, 26, 7, 50, 5, 51, 16, 20, 16, 40, 5, 56, 11, 32, 19, 59, 3
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OFFSET
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1,7
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COMMENTS
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30 is the largest number n with the property that if 1 < k < n and k is relatively prime to n, then k is prime. In other words, a(30) = 0 and if m > 30, then a(m) > 0. - Jonathan Sondow, Dec 08 2012
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LINKS
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FORMULA
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MATHEMATICA
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Table[ Count[ Select[ Range[ n ], GCD[ #, n ]===1& ], q_/; !(PrimeQ[ q ]||q===1) ], {n, 180} ]
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CROSSREFS
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Cf. A048597 (indices where a(n) = 0), A048865 (number of primes p < n that are relatively prime to n).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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