A048033 Number of nonempty subsets of {1,2,...,n} in which exactly 2/5 of the elements are <= (n-3)/3.

0, 0, 0, 0, 0, 0, 0, 0, 35, 56, 84, 252, 360, 495, 1452, 2244, 3432, 11440, 18655, 29575, 86905, 139960, 220150, 617610, 1007216, 1616615, 4563344, 7573970, 12359690, 34220634, 57059772, 93595740, 254222289, 425926604, 703601510