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Search: id:A056811
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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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+0
3
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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
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OFFSET
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1,9
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COMMENT
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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].
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FORMULA
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a(n)=A056170[A003418)]=A000720[A000196(n)]
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EXAMPLE
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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
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A056170, A003418, A000720, A000196.
Sequence in context: A082998 A076620 A121900 this_sequence A097430 A054900 A046042
Adjacent sequences: A056808 A056809 A056810 this_sequence A056812 A056813 A056814
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Aug 28 2000
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