A048065 - OEIS

A048065

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

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

%S 0,0,0,0,0,5,15,30,70,105,213,286,558,720,1500,1935,4455,5775,13895,

%T 17876,42484,53859,124761,156065,357825,444015,1028500,1272155,

%U 3002795,3709043,8871603,10935267,26243427

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

%K nonn

%O 1,6

%A _Clark Kimberling_