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 A120040 #7 Jul 06 2012 11:43:47
%S A120040 0,0,0,0,0,0,0,0,1,1,5,8,22,47,102,232,482,1062,2217,4738,10051,21083,
%T A120040 44315,92608,193824,402936,838879,1739794,3605077,7457977,15404202,
%U A120040 31781036,65481376,134777594,277096118,569173839,1168002568,2394834166
%N A120040 Number of 9-almost primes 9ap such that 2^n < 9ap <= 2^(n+1).
%C A120040 The partial sum equals the number of Pi_9(2^n).
%e A120040 (2^9, 2^10] there is one semiprime, namely 768. 512 was counted in the previous entry.
%t A120040 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 A120040 t = Table[AlmostPrimePi[9, 2^n], {n, 0, 30}]; Rest@t - Most@t
%Y A120040 Cf. A046312, A036378, A120033, A120034, A120035, A120036, A120037, A120038, A120039, A120040, A120041, A120042, A120043.
%K A120040 nonn
%O A120040 0,11
%A A120040 _Jonathan Vos Post_ and _Robert G. Wilson v_, Mar 21 2006