a(n) = 3^n*(n + 2)!.A153647a(n) = 3^n*(n + 2)!.Terms a(0) =2a(1) =18a(2) =216a(3) =3240a(4) =58320a(5) =1224720a(6) =29393280a(7) =793618560a(8) =23808556800a(9) =785682374400External referencesoeis: A153647