%I A018806
%S A018806 1,5,12,24,37,61,80,112,145,189,220,288,325,389,464,544,593,701,756,880,
%T A018806 989,1093,1160,1336,1441,1565,1700,1880,1965,2205,2296,2488,2665,2829,
%U A018806 3028,3328,3437,3621,3832,4152,4273,4621,4748,5040,5373,5597,5736,6168
%N A018806 Sum of gcd(x, y) for 1 <= x, y <= n.
%F A018806 Sum_{k=1..n} phi(k)*(floor(n/k))^2. - Vladeta Jovovic (vladeta(AT)eunet.rs), 
               Nov 10 2002
%Y A018806 Cf. A000010, A018805, A064951.
%Y A018806 Sequence in context: A066869 A023172 A100479 this_sequence A126880 A108314 
               A079425
%Y A018806 Adjacent sequences: A018803 A018804 A018805 this_sequence A018807 A018808 
               A018809
%K A018806 nonn
%O A018806 1,2
%A A018806 David W. Wilson (davidwwilson(AT)comcast.net)