a(n) = 3^n*n^4.

Terms

a(0) =0a(1) =3a(2) =144a(3) =2187a(4) =20736a(5) =151875a(6) =944784a(7) =5250987a(8) =26873856a(9) =129140163a(10) =590490000a(11) =2593609227a(12) =11019960576a(13) =45535459203a(14) =183742537104a(15) =726413416875