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 A144741 Partial cototient function Phi(c, n) for c = 2: number of semiprimes less than or equal and not coprime to n. 4
 0, 0, 0, 1, 0, 2, 0, 2, 2, 3, 0, 4, 0, 4, 4, 4, 0, 6, 0, 5, 5, 5, 0, 8, 3, 6, 4, 7, 0, 10, 0, 6, 6, 7, 6, 11, 0, 8, 7, 11, 0, 14, 0, 9, 9, 9, 0, 14, 4, 12, 8, 10, 0, 15, 7, 12, 9, 10, 0, 20, 0, 11, 11, 11, 8, 19, 0, 12, 10, 18, 0, 19, 0, 12, 14, 13, 8, 21, 0, 17, 9, 13, 0, 24, 9, 14, 11, 17, 0, 28, 9 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS EXAMPLE Phi(2, 4) = 1: four is a semiprime. Phi(2, 10) = 3: four, six and ten are semiprimes; nine is a semiprime relatively prime to ten. CROSSREFS Cf. A000010, A144740 Sequence in context: A103863 A166395 A061199 * A103615 A308167 A293665 Adjacent sequences:  A144738 A144739 A144740 * A144742 A144743 A144744 KEYWORD easy,nonn AUTHOR Reikku Kulon, Sep 20 2008 STATUS approved

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Last modified May 27 06:24 EDT 2019. Contains 323599 sequences. (Running on oeis4.)