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A070803
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Number of primes not exceeding sum of divisors of n.
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8
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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; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| a(n)=A000720[A000203(n)]=Pi[sigma[n]]
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EXAMPLE
| n=50: sigma[50]=93, Pi[93]=24=a(50)
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MATHEMATICA
| Table[PrimePi[DivisorSigma[1, n]], {n, 1, 256}]
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PROG
| (Other) sage: [prime_pi(sigma(n, 1)) for n in xrange(1, 76)] # [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 06 2009]
(PARI) A070803(n) = primepi(sigma(n)) [From Michael B. Porter (michael_b_porter(AT)yahoo.com), Jan 28 2010]
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CROSSREFS
| Cf. A007818, A000203, A000720, A070800-A070804.
Sequence in context: A145393 A132802 A204900 * A071693 A007728 A077026
Adjacent sequences: A070800 A070801 A070802 * A070804 A070805 A070806
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KEYWORD
| easy,nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), May 08 2002
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