A120052 Number of 11-almost primes less than or equal to 10^n.

0, 0, 0, 0, 7, 138, 1878, 23448, 279286, 3230577, 36585097, 407818620, 4490844534, 48972151631, 529781669333

Offset

0,5

Links

Table of n, a(n) for n=0..14.

Example

There are 7 eleven-almost primes up to 10000: 2048, 3072, 4608, 5120, 6912, 7168 & 7680.

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[11, 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: A221342 A221298 A009701 * A171106 A217504 A375009

Adjacent sequences: A120049 A120050 A120051 * A120053 A120054 A120055

Keyword

nonn

Author

Robert G. Wilson v, Feb 07 2006

Extensions

a(14) from Robert G. Wilson v, Jan 07 2007

Status

approved