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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =3a(6) =6a(7) =24a(8) =40a(9) =100a(10) =150a(11) =315a(12) =455a(13) =980a(14) =1470a(15) =3528a(16) =5544a(17) =13692a(18) =21630a(19) =51600a(20) =80520a(21) =186945a(22) =290400a(23) =675675a(24) =1056627a(25) =2492919a(26) =3929926a(27) =9324406a(28) =14742910a(29) =34860553