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Number of nonempty subsets of {1,2,...,n} in which exactly 2/5 of the elements are <= (n-1)/2.
0

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

%S 0,0,0,0,1,4,12,30,60,121,205,385,630,1260,2156,4711,8260,18340,31620,

%T 68772,115995,250185,418825,914485,1535391,3405402,5728086,12788516,

%U 21448791,47902764,80006668,178864378,298009048,668688388

%N Number of nonempty subsets of {1,2,...,n} in which exactly 2/5 of the elements are <= (n-1)/2.

%K nonn

%O 1,6

%A _Clark Kimberling_