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%I #4 Mar 30 2012 18:56:54
%S 0,0,1,2,3,9,12,15,40,51,63,175,220,270,759,945,1155,3311,4102,5005,
%T 14547,17955,21875,64275,79116,96288,285413,350568,426303,1272601,
%U 1560449,1896279,5694129,6972339,8468163,25554035,31253950
%N Number of nonempty subsets of {1,2,...,n} in which exactly 2/3 of the elements are <= (n+3)/3.
%K nonn
%O 1,4
%A _Clark Kimberling_