%I A072747
%S A072747 0,1,1,1,2,2,3,3,3,4,4,4,4,4,5,5,6,6,7,7,7,8,8,8,9,9,9,10,10,11,11,11,
%T A072747 11,11,11,12,12,12,13,13,14,14,14,15,15,15,16,16,17,17,18,18,18,19,19,
%U A072747 19,19,19,20,20,20,20,21,21,21,22,22,22,23,23,23,24,24,25,25,26,26,26
%N A072747 Counting factor 2 in square-free numbers <=n.
%e A072747 The first 10 square-free numbers are: 1, 2, 3, 5, 6=2*3, 7, 10=2*5, 11, 
               13 and 14=2*7
%e A072747 2, 6, 10 and 14 are divisible by 2, therefore a(10)=4.
%Y A072747 Cf. A005117, A072748, A072749, A072750, A072751.
%Y A072747 Sequence in context: A143824 A034463 A071996 this_sequence A124755 A033810 
               A023965
%Y A072747 Adjacent sequences: A072744 A072745 A072746 this_sequence A072748 A072749 
               A072750
%K A072747 nonn
%O A072747 1,5
%A A072747 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 08 2002