Convolution of 2^n*n! and n!.

Terms

a(0) =1a(1) =3a(2) =12a(3) =66a(4) =484a(5) =4536a(6) =52128a(7) =709776a(8) =11153376a(9) =198339840a(10) =3932962560a(11) =85976743680