a(n) = A003474(n)/n.

Terms

a(0) =1a(1) =2a(2) =6a(3) =8a(4) =32a(5) =54a(6) =208a(7) =256a(8) =1458a(9) =2560a(10) =10648a(11) =17496a(12) =70304a(13) =151424a(14) =629856a(15) =819200a(16) =5064320a(17) =9565938a(18) =40781104a(19) =65536000a(20) =331619184a(21) =623589472a(22) =2728756984a(23) =3673320192a(24) =22315420160a(25) =32127240704a(26) =188286357654a(27) =321009188864