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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =21a(10) =28a(11) =112a(12) =144a(13) =360a(14) =450a(15) =1110a(16) =1430a(17) =4235a(18) =5775a(19) =17556a(20) =24388a(21) =68328a(22) =94731a(23) =251160a(24) =349300a(25) =923230a(26) =1301080a(27) =3482710a(28) =4976070a(29) =13287846