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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =5a(8) =6a(9) =24a(10) =28a(11) =70a(12) =80a(13) =188a(14) =216a(15) =567a(16) =665a(17) =1820a(18) =2156a(19) =5709a(20) =6772a(21) =17500a(22) =20800a(23) =53911a(24) =64372a(25) =168245a(26) =201785a(27) =527540a(28) =634556a(29) =1652924