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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =3a(6) =4a(7) =5a(8) =20a(9) =24a(10) =28a(11) =70a(12) =80a(13) =90a(14) =216a(15) =245a(16) =275a(17) =770a(18) =882a(19) =1001a(20) =2912a(21) =3332a(22) =3780a(23) =10535a(24) =11984a(25) =13532a(26) =37400a(27) =42450a(28) =47880a(29) =135432