First diagonal of A027518.

Terms

a(0) =1a(1) =1a(2) =8a(3) =54a(4) =13500a(5) =3087000a(6) =3652264a(7) =1157625a(8) =456533a(9) =166375a(10) =4492125a(11) =1728000a(12) =394444512000