id:A070804 - OEIS Search Results

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Number of primes not exceeding phi[n].

+0
9

0, 0, 1, 1, 2, 1, 3, 2, 3, 2, 4, 2, 5, 3, 4, 4, 6, 3, 7, 4, 5, 4, 8, 4, 8, 5, 7, 5, 9, 4, 10, 6, 8, 6, 9, 5, 11, 7, 9, 6, 12, 5, 13, 8, 9, 8, 14, 6, 13, 8, 11, 9, 15, 7, 12, 9, 11, 9, 16, 6, 17, 10, 11, 11, 15, 8, 18, 11, 14, 9, 19, 9, 20, 11, 12, 11, 17, 9, 21, 11, 16, 12, 22, 9, 18, 13, 16 (list; graph; listen)

	OFFSET	`1,5`
	FORMULA	`a(n)=A000720[A000010(n)]=Pi[phi[n]]`
	EXAMPLE	`n=50: phi[50]=20,Pi[20]=8=a(50)`
	MATHEMATICA	`Table[PrimePi[EulerPhi[n]], {n, 1, 256}]`
	CROSSREFS	`Cf. A007818, A000010, A000720, A070800-A070804.` `Sequence in context: A110917 A070956 A007828 this_sequence A104481 A078709 A023022` `Adjacent sequences: A070801 A070802 A070803 this_sequence A070805 A070806 A070807`
	KEYWORD	`easy,nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), May 08 2002`

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Last modified December 10 12:37 EST 2009. Contains 170569 sequences.

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