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Number of nonempty subsets of {1,2,...,n} in which exactly 2/3 of the elements are <= (n+1)/3.
0

%I #4 Mar 30 2012 18:56:54

%S 0,0,0,0,3,4,5,15,18,21,63,76,90,270,325,385,1155,1390,1651,5005,6027,

%T 7175,21875,26348,31416,96288,116010,138510,426303,513729,614019,

%U 1896279,2285569,2734171,8468163,10208110,12220780,37941280

%N Number of nonempty subsets of {1,2,...,n} in which exactly 2/3 of the elements are <= (n+1)/3.

%K nonn

%O 1,5

%A _Clark Kimberling_