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

Terms

a(0) =0a(1) =4a(2) =256a(3) =5184a(4) =65536a(5) =640000a(6) =5308416a(7) =39337984a(8) =268435456a(9) =1719926784a(10) =10485760000a(11) =61408804864a(12) =347892350976