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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =15a(9) =21a(10) =28a(11) =112a(12) =144a(13) =180a(14) =450a(15) =550a(16) =660a(17) =1815a(18) =2275a(19) =2821a(20) =10192a(21) =13230a(22) =16940a(23) =57680a(24) =74256a(25) =94248a(26) =288456a(27) =367080a(28) =461700a(29) =1427850