|
Search: id:A120048
|
|
|
| A120048 |
|
Number of 7-almost primes less than or equal to 10^n. |
|
+0
10
|
|
| 0, 0, 0, 14, 231, 2973, 35585, 409849, 4600247, 50678212, 550454756, 5913771637, 62981797962, 665997804082, 7001087934965
(list; graph; listen)
|
|
|
OFFSET
|
0,4
|
|
|
EXAMPLE
|
There are 7 seven-almost primes up to 100: 128, 192, 288, 320, 432, 448, 480, 648, 672, 704, 720, 800, 832 & 972.
|
|
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 (eww(AT)wolfram.com) Feb 07 2006 *)
Table[AlmostPrimePi[7, 10^n], {n, 11}]
|
|
CROSSREFS
|
Cf. A066265, A014613, A116382.
Cf. A006880, A036352, A109251, A114106, A114453, A120047, A120048, A120049, A120050, A120051, A120052, A120053, A116430.
Sequence in context: A145269 A027774 A099272 this_sequence A079563 A166774 A055477
Adjacent sequences: A120045 A120046 A120047 this_sequence A120049 A120050 A120051
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 07 2006
|
|
EXTENSIONS
|
More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 07 2007
|
|
|
Search completed in 0.002 seconds
|
