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 A120049 Number of 8-almost primes less than or equal to 10^n. 12
 0, 0, 0, 7, 105, 1418, 17572, 207207, 2367507, 26483012, 291646797, 3173159326, 34192782745, 365561221293, 3882841742380 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS EXAMPLE There are 7 eight-almost primes up to 1000: 256, 384, 576, 640, 864, 896 & 960. MATHEMATICA 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, Feb 07 2006 *) Table[AlmostPrimePi[8, 10^n], {n, 12}] CROSSREFS Cf. A066265, A014613, A116382. Cf. A006880, A036352, A109251, A114106, A114453, A120047, A120048, A120049, A120050, A120051, A120052, A120053, A116430. Sequence in context: A098362 A093741 A139742 * A067420 A131869 A132867 Adjacent sequences:  A120046 A120047 A120048 * A120050 A120051 A120052 KEYWORD nonn AUTHOR Robert G. Wilson v, Feb 07 2006 EXTENSIONS a(13) and a(14) from Robert G. Wilson v, Jan 07 2007 Example corrected by Harvey P. Dale, Aug 13 2018 STATUS approved

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Last modified July 31 00:50 EDT 2021. Contains 346365 sequences. (Running on oeis4.)