%I A111939
%S A111939 2,3,4,4,6,6,8,8,9,9,11,11,11,12,12,14,15,15,16,16,16,18,18,19,21,21,22,
%T A111939 23,23,23,24,24,24,24,27,29,30,30,30,30,30,30,31,32,32,34,34,34,34,34,
%U A111939 36,37,37,37,38,39,40,40,42,42,42,44,46,46,46,46,46,46,47,47,47,47,47
%N A111939 Number of primes < semiprime(n).
%F A111939 a(n) = A000720(A001358(n)).
%t A111939 PrimePi@Select[Range@218, Plus @@ Last /@ FactorInteger@# == 2 &] (from 
               Robert G. Wilson v (rgwv(at)rgwv.com), Jan 10 2006)
%Y A111939 Cf. A122489.
%Y A111939 Sequence in context: A063208 A092988 A138768 this_sequence A003962 A102443 
               A102441
%Y A111939 Adjacent sequences: A111936 A111937 A111938 this_sequence A111940 A111941 
               A111942
%K A111939 nonn
%O A111939 1,1
%A A111939 Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Nov 27 2005
%E A111939 More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Lambert Herrgesell 
               (zero815(AT)googlemail.com) and Matthew Conroy (http://www.madandmoonly.com/
               doctormatt), Dec 16 2005
%E A111939 Entry revised by Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 20 
               2006