A diagonal of square array A192404.

Terms

a(0) =1a(1) =4a(2) =31a(3) =291a(4) =3092a(5) =35839a(6) =441925a(7) =5721008a(8) =77009425a(9) =1071034612a(10) =15319883964a(11) =224628789200