%I A064027
%S A064027 1,3,10,19,26,30,50,83,91,78,122,190,170,150,260,339,290,273,362,494,
%T A064027 500,366,530,830,651,510,820,950,842,780,962,1363,1220,870,1300,1729,
%U A064027 1370,1086,1700,2158,1682,1500,1850,2318,2366,1590,2210,3390,2451,1953
%N A064027 a(n) = (-1)^n*Sum_{d|n}(-1)^d*d^2.
%F A064027 Multiplicative with a(2^e) = (4^(e+1)-7)/3, a(p^e) = (p^(2*e+2)-1)/(p^2-1), 
               p > 2. a(n) = (-1)^n*(A001157(n)-2*A050999(n)).
%Y A064027 Cf. A002129, A008457.
%Y A064027 Sequence in context: A074893 A074178 A127852 this_sequence A028878 A010896 
               A135446
%Y A064027 Adjacent sequences: A064024 A064025 A064026 this_sequence A064028 A064029 
               A064030
%K A064027 mult,nonn
%O A064027 1,2
%A A064027 Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 11 2001