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

%I #5 Mar 30 2012 18:56:53

%S 0,0,0,0,3,4,12,15,40,51,135,175,455,596,1540,2037,5250,7000,18000,

%T 24156,62007,83667,214467,290719,744315,1012935,2590679,3537703,

%U 9039823,12381252,31612324,43411489,110761494,152459010

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

%K nonn

%O 1,5

%A _Clark Kimberling_