Number of nonempty subsets of {1,2,...,n} in which exactly 5/6 of the elements are <= (n-1)/2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =0a(10) =6a(11) =7a(12) =42a(13) =48a(14) =168a(15) =189a(16) =504a(17) =560a(18) =1260a(19) =1386a(20) =2827a(21) =3090a(22) =6270a(23) =6864a(24) =15444a(25) =17094a(26) =44044a(27) =49335a(28) =135135a(29) =152152