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A120053 Number of 12-almost primes less than or equal to 10^n. 10
0, 0, 0, 0, 3, 63, 865, 11068, 133862, 1563465, 17836903, 200051717, 2214357712, 24255601105, 263439785143 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,5
LINKS
EXAMPLE
There are 3 twelve-almost primes up to 10000: 4096, 6144 & 9216.
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[12, 10^n], {n, 11}]
CROSSREFS
Sequence in context: A048354 A046181 A151993 * A139293 A370827 A133275
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Feb 07 2006
EXTENSIONS
a(13) and a(14) from Robert G. Wilson v, Jan 07 2007
STATUS
approved

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Last modified July 20 17:48 EDT 2024. Contains 374459 sequences. (Running on oeis4.)