Search: id:A127396
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%I A127396
%S A127396 0,0,1,2,7,13,30,60,125,256,513,1049,2082,4214,8401,16771,33427,66550,
%T A127396 132405,262865,522296,1036033,2055256,4075039,8078110,16008485,31720903,
%U A127396 62847087,124501149,246638355,488559079,967785236,1917099175,3797688543
%N A127396 Number of 3-almostprimes <= 2^n.
%H A127396 Robert G. Wilson v, <a href="b127396.txt">Table of n, a(n) for n = 1..49</
               a>
%H A127396 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               Semiprime.html">Link to a section of The World of Mathematics</a>
               .
%t A127396 ThreeAlmostPrimePi[n_] := Sum[PrimePi[n/(Prime@i*Prime@j)] - j + 1, {i, 
               PrimePi[n^(1/3)]}, {j, i, PrimePi[Sqrt[n/Prime@i]]}]; Table[ ThreeAlmostPrimePi[2^n], 
               {n, 30}]
%Y A127396 Cf. A126279, A109251, A125527.
%Y A127396 Sequence in context: A045376 A045377 A141777 this_sequence A079119 A051748 
               A086904
%Y A127396 Adjacent sequences: A127393 A127394 A127395 this_sequence A127397 A127398 
               A127399
%K A127396 nonn,less
%O A127396 1,4
%A A127396 Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 29 2006

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