id:A079715 - OEIS Search Results

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a(n) = Pi(n)-Pi(sqrt(n)) + 1

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	OFFSET	`1,2`
	COMMENT	`a(n)=sum( d' dividing n, mu(d')*floor(n/d')) where each prime factor of d' is <=sqrt(n).` `A well-known application of the principle of inclusion-exclusion used in sieve methods.` `Number of numbers less than or equal to n and coprime to the product of the primes less than sqrt(n), i.e. to A104588(n). - Lekraj Beedassy (blekraj(AT)yahoo.com), Mar 17 2005`
	FORMULA	`a(n) = pi(n) - pi(sqrt(n)) + 1 = A000720(n) - A056811(n) + 1 = A056812(n) + 1.`
	CROSSREFS	`Cf. A000720, A056811.` `Sequence in context: A086389 A128622 A026256 this_sequence A030397 A082597 A112212` `Adjacent sequences: A079712 A079713 A079714 this_sequence A079716 A079717 A079718`
	KEYWORD	`nonn`
	AUTHOR	`Benoit Cloitre (benoit7848c(AT)orange.fr), Feb 16 2003`
	EXTENSIONS	`Edited by N. J. A. Sloane (njas(AT)research.att.com) at the suggestion of Andrew Plewe, Jun 12 2007`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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