Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n-1)/3.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =0a(10) =0a(11) =0a(12) =9a(13) =10a(14) =11a(15) =55a(16) =60a(17) =65a(18) =195a(19) =210a(20) =225a(21) =525a(22) =560a(23) =595a(24) =1326a(25) =1413a(26) =1501a(27) =3933a(28) =4230a(29) =4536