Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 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) =0a(10) =0a(11) =8a(12) =9a(13) =45a(14) =50a(15) =150a(16) =165a(17) =385a(18) =420a(19) =906a(20) =988a(21) =2340a(22) =2583a(23) =7035a(24) =7875a(25) =22275a(26) =25080a(27) =67880a(28) =76415a(29) =196027