%I
%S 1,1,1,0,0,3,3,5,6,9,9,15,15,18,21,24,24,30,30,36,39,42,42,51,52,55,
%T 57,63,63,75,75,79,82,85,88,99,99,102,105,114,114,126,126,132,138,141,
%U 141,153,154,160,163,169,169,178,181,190,193,196,196,217,217,220,226
%N Let G be the graph with n vertices, the ith vertex consisting of all multiples of i <= n, where edges indicate that the vertices intersect; a(n) = n(number of edges of G).
%e For n=6 the vertices are {1,2,3,4,5,6},{2,4,6},{3,6},{4},{5},{6}. There are 9 = 5+3+1 edges and so a(6) = 69 = 3.
%K nonn
%O 1,6
%A _Stephen P. Humphries_
