This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A120052 #16 Mar 20 2025 06:00:19
%S A120052 0,0,0,0,7,138,1878,23448,279286,3230577,36585097,407818620,
%T A120052 4490844534,48972151631,529781669333,5693047157230,60832290450373,
%U A120052 646862625625663,6849459596884350,72259172519243461
%N A120052 Number of 11-almost primes less than or equal to 10^n.
%e A120052 There are 7 eleven-almost primes up to 10000: 2048, 3072, 4608, 5120, 6912, 7168, and 7680.
%t A120052 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 *)
%t A120052 Table[AlmostPrimePi[11, 10^n], {n, 12}]
%Y A120052 Cf. A066265, A014613, A116382.
%Y A120052 Cf. A006880, A036352, A109251, A114106, A114453, A120047, A120048, A120049, A120050, A120051, A120052, A120053, A116430.
%K A120052 nonn,more
%O A120052 0,5
%A A120052 _Robert G. Wilson v_, Feb 07 2006
%E A120052 a(14) from _Robert G. Wilson v_, Jan 07 2007
%E A120052 a(15)-a(19) from _Henri Lifchitz_, Mar 18 2025