A047179 - OEIS

A047179

Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n-1)/2.

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

%S 0,0,0,0,0,0,0,0,5,6,30,35,105,120,280,315,666,745,1665,1881,4785,

%T 5490,14850,17160,45331,52339,131859,151775,371735,427336,1048840,

%U 1207765,3021240,3490050

%N Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n-1)/2.

%K nonn

%O 1,9

%A _Clark Kimberling_