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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =10a(8) =15a(9) =60a(10) =84a(11) =210a(12) =280a(13) =630a(14) =846a(15) =2142a(16) =3045a(17) =8400a(18) =12320a(19) =32802a(20) =48048a(21) =121110a(22) =176670a(23) =437580a(24) =642642a(25) =1608607a(26) =2391895a(27) =6034600a(28) =9050470a(29) =22712326