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Search: id:A120047
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| A120047 |
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Number of 6-almost primes less than or equal to 10^n. |
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+0
10
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| 0, 0, 2, 37, 485, 5933, 68963, 774078, 8493366, 91683887, 977694273, 10327249593, 108264085934, 1128049914377, 11694704489580
(list; graph; listen)
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OFFSET
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0,3
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EXAMPLE
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There are 2 six-almost primes up to 100: 64 & 96.
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MATHEMATICA
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AlmostPrimePi[k_Integer, n_] := Module[{a, i}, a[0] = 1; If[k == 1, PrimePi[n], Sum[PrimePi[n/Times @@ Prime[Array[a, k - 1]]] - a[k - 1] + 1, Evaluate[ Sequence @@ Table[{a[i], a[i - 1], PrimePi[(n/Times @@ Prime[Array[a, i - 1]])^(1/(k - i + 1))]}, {i, k - 1}]]]]]; (* Eric W.Weisstein (eww(AT)wolfram.com) Feb 07 2006 *)
Table[AlmostPrimePi[6, 10^n], {n, 0, 13}]
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CROSSREFS
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Cf. A066265, A014613, A116382.
Cf. A006880, A036352, A109251, A114106, A114453, A120047, A120048, A120049, A120050, A120051, A120052, A120053, A116430.
Sequence in context: A001569 A092853 A100849 this_sequence A139122 A123216 A058245
Adjacent sequences: A120044 A120045 A120046 this_sequence A120048 A120049 A120050
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KEYWORD
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nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 07 2006
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EXTENSIONS
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a(14) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 07 2007
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