Number of black-white-balanced permutations of [n].

Terms

a(0) =0a(1) =0a(2) =4a(3) =16a(4) =0a(5) =0a(6) =2592a(7) =20736a(8) =0a(9) =0a(10) =17280000a(11) =207360000a(12) =0a(13) =0a(14) =497871360000a(16) =0a(17) =0a(20) =0a(21) =0a(24) =0a(25) =0