A048065 Number of nonempty subsets of {1,2,...,n} in which exactly 1/5 of the elements are <= (n-4)/2.

0, 0, 0, 0, 0, 5, 15, 30, 70, 105, 213, 286, 558, 720, 1500, 1935, 4455, 5775, 13895, 17876, 42484, 53859, 124761, 156065, 357825, 444015, 1028500, 1272155, 3002795, 3709043, 8871603, 10935267, 26243427