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

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =3a(6) =6a(7) =10a(8) =40a(9) =60a(10) =84a(11) =210a(12) =280a(13) =360a(14) =846a(15) =1110a(16) =1430a(17) =4235a(18) =5775a(19) =7735a(20) =24388a(21) =33124a(22) =44100a(23) =128485a(24) =170968a(25) =223720a(26) =639880a(27) =846600a(28) =1105800a(29) =3311187