a(n) = n^2*4^n.

Terms

a(0) =0a(1) =4a(2) =64a(3) =576a(4) =4096a(5) =25600a(6) =147456a(7) =802816a(8) =4194304a(9) =21233664a(10) =104857600a(11) =507510784a(12) =2415919104a(13) =11341398016a(14) =52613349376a(15) =241591910400