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A056811
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Number of primes not exceeding square root of n: PrimePi[Sqrt(n)];.
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2
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0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,9
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COMMENTS
| Number of primes among factors of LCM[1,..,n] whose exponent is > 1, i.e. number of non unitary prime factors of LCM[1,..,n].
Number of positive integers <= n with exactly 3 divisors.
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FORMULA
| a(n)=A056170[A003418)]=A000720[A000196(n)]
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EXAMPLE
| If n=169,...,288=p()^2,..,p(7)^2-1, then only the first 6 primes have exponents larger than 1, resulting in powers: 128,81,125,49,121,169. So a(n)=6 for as much as 288-169+1=120 values of n.
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CROSSREFS
| Cf. A056170, A003418, A000720, A000196.
Sequence in context: A082998 A076620 A121900 * A097430 A054900 A046042
Adjacent sequences: A056808 A056809 A056810 * A056812 A056813 A056814
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Aug 28 2000
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