a(n) = A203418(n)/A000178(n).

Terms

a(0) =1a(1) =2a(2) =8a(3) =20a(4) =40a(5) =384a(6) =10240a(7) =126720a(8) =1013760a(9) =48660480a(10) =7612661760a(11) =473174507520