id:A070803 - OEIS Search Results

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Number of primes not exceeding sum of divisors of n.

+0
8

0, 2, 2, 4, 3, 5, 4, 6, 6, 7, 5, 9, 6, 9, 9, 11, 7, 12, 8, 13, 11, 11, 9, 17, 11, 13, 12, 16, 10, 20, 11, 18, 15, 16, 15, 24, 12, 17, 16, 24, 13, 24, 14, 23, 21, 20, 15, 30, 16, 24, 20, 25, 16, 30, 20, 30, 22, 24, 17, 39, 18, 24, 27, 31, 23, 34, 19, 30, 24, 34, 20, 44, 21, 30, 30 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`a(n)=A000720[A000203(n)]=Pi[sigma[n]]`
	EXAMPLE	`n=50: sigma[50]=93, Pi[93]=24=a(50)`
	MATHEMATICA	`Table[PrimePi[DivisorSigma[1, n]], {n, 1, 256}]`
	PROGRAM	`(Other) sage: [prime_pi(sigma(n, 1)) for n in xrange(1, 76)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 06 2009]`
	CROSSREFS	`Cf. A007818, A000203, A000720, A070800-A070804.` `Sequence in context: A054346 A145393 A132802 this_sequence A071693 A007728 A077026` `Adjacent sequences: A070800 A070801 A070802 this_sequence A070804 A070805 A070806`
	KEYWORD	`easy,nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), May 08 2002`

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Last modified November 25 14:49 EST 2009. Contains 167514 sequences.

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