%I A068074
%S A068074 1,1,3,1,3,3,3,3,5,3,3,3,3,3,9,5,3,5,3,3,9,3,3,9,5,3,7,3,3,9,3,7,9,3,9,
%T A068074 5,3,3,9,9,3,9,3,3,15,3,3,15,5,5,9,3,3,7,9,9,9,3,3,9,3,3,15,9,9,9,3,3,
%U A068074 9,9,3,15,3,3,15,3,9,9,3,15,9,3,3,9,9,3,9,9,3,15,9,3,9,3,9
%V A068074 -1,-1,-3,1,-3,-3,-3,3,-5,-3,-3,3,-3,-3,-9,5,-3,-5,-3,3,-9,-3,-3,9,-5,
               -3,-7,3,-3,-9,
%W A068074 -3,7,-9,-3,-9,5,-3,-3,-9,9,-3,-9,-3,3,-15,-3,-3,15,-5,-5,-9,3,-3,-7,-9,
               9,-9,-3,-3,9,
%X A068074 -3,-3,-15,9,-9,-9,-3,3,-9,-9,-3,15,-3,-3,-15,3,-9,-9,-3,15,-9,-3,-3,9,
               -9,-3,-9,9,-3
%N A068074 a(n)=sum(d|n,(-1)^d*2^omega(n/d)) where omega(x) is the number of distinct 
               prime factors in x factorization.
%D A068074 G. Tenenbaum and Jie Wu, Cours specialies No. 2: "Exercices corriges 
               de theorie analytique et probabiliste des nombres", Collection SMF, 
               chap. II.7.1, p. 105.
%F A068074 Asymptotic formula : sum(k=1, n, a(k)/k)=-C*ln(n)^2 with C=3*ln(2)/Pi^2
%F A068074 a(n) = -tau(n^2) for odd n and 2*tau(n^2/4)-tau(n^2) for even n. b(n) 
               = abs(a(n)) is multiplicative with b(2^e) = abs(2*e-3) and b(p^e) 
               = 2*e+1 for an odd prime p. - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Apr 25 2002
%Y A068074 Cf. A048691.
%Y A068074 Sequence in context: A059789 A023136 A152774 this_sequence A063195 A025796 
               A024163
%Y A068074 Adjacent sequences: A068071 A068072 A068073 this_sequence A068075 A068076 
               A068077
%K A068074 easy,nice,sign
%O A068074 1,3
%A A068074 Benoit Cloitre (benoit7848c(AT)orange.fr), Apr 14 2002