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%I
%S 0,0,0,1,1,1,1,1,2,2,2,3,3,4,4,5,5,5,6,6,6,6,6,7,8,8,8,9,10,10,10,10,
%T 11,11,11,12,12,13,14,15,15,15,15,16,16,16,16,16,17,18,19,20,20,20,20,
%U 20,21,21,22,23,23,23,23,24,24,24,25,25,25,25,25,26,27,28,28,28,29,29
%N Number of x with largest prime factor of the form 4k+1 less than or equal to n.
%C Conjecture : for n > 1000 a(n) - n/2 < - sqrt(n) ( if b(n) denotes the number of x with largest prime factor of the form 4k+3 less than or equal to n, it is conjectured that if n > 1000 b(n)- n/2 > sqrt(n) )
%o (PARI) for(n=2,200,print1(sum(i=2,n,if((component(component(factor(i),1),omega(i))-1)%4,0,1)),","))
%K easy,nonn
%O 1,9
%A _Benoit Cloitre_, Jun 07 2002
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