Number of nonempty subsets of {1,2,...,n} in which exactly 1/6 of the elements are <= (n-4)/2.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =1a(6) =6a(7) =12a(8) =42a(9) =63a(10) =168a(11) =224a(12) =504a(13) =630a(14) =1270a(15) =1527a(16) =2937a(17) =3465a(18) =6930a(19) =8184a(20) =18304a(21) =21879a(22) =54054a(23) =65065a(24) =165285a(25) =198363a(26) =491128a(27) =584464a(28) =1387744a(29) =1636284