A048011 Number of nonempty subsets of {1,2,...,n} in which exactly 2/5 of the elements are <= (n-1)/3.

0, 0, 0, 0, 0, 0, 10, 20, 35, 105, 168, 252, 588, 930, 1452, 3960, 6820, 11440, 30745, 52507, 86905, 219765, 372120, 617610, 1572228, 2702252, 4563344, 11666760, 20167170, 34220634, 86461704, 149465844, 254222289, 639438019