%I A120053
%S A120053 0,0,0,0,3,63,865,11068,133862,1563465,17836903,200051717,2214357712,
%T A120053 24255601105,263439785143
%N A120053 Number of 12-almost primes less than or equal to 10^n.
%e A120053 There are 3 twelve-almost primes up to 10000: 4096, 6144 & 9216.
%t A120053 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 *)
%t A120053 Table[AlmostPrimePi[12, 10^n], {n, 11}]
%Y A120053 Cf. A066265, A014613, A116382.
%Y A120053 Cf. A006880, A036352, A109251, A114106, A114453, A120047, A120048, A120049, 
               A120050, A120051, A120052, A120053, A116430.
%Y A120053 Sequence in context: A048354 A046181 A151993 this_sequence A139293 A133275 
               A123687
%Y A120053 Adjacent sequences: A120050 A120051 A120052 this_sequence A120054 A120055 
               A120056
%K A120053 nonn
%O A120053 0,5
%A A120053 Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 07 2006
%E A120053 a(13) and a(14) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 07 2007