a(n) = 204*2^n - 248.

Terms

a(0) =160a(1) =568a(2) =1384a(3) =3016a(4) =6280a(5) =12808a(6) =25864a(7) =51976a(8) =104200a(9) =208648a(10) =417544a(11) =835336a(12) =1670920a(13) =3342088a(14) =6684424a(15) =13369096a(16) =26738440a(17) =53477128a(18) =106954504a(19) =213909256a(20) =427818760a(21) =855637768a(22) =1711275784a(23) =3422551816a(24) =6845103880a(25) =13690208008a(26) =27380416264a(27) =54760832776