a(n) = 6*a(n-1) - 8*a(n-2) for n > 1; a(0) = 6, a(1) = 28.

Terms

a(0) =6a(1) =28a(2) =120a(3) =496a(4) =2016a(5) =8128a(6) =32640a(7) =130816a(8) =523776a(9) =2096128a(10) =8386560a(11) =33550336a(12) =134209536a(13) =536854528a(14) =2147450880a(15) =8589869056a(16) =34359607296a(17) =137438691328a(18) =549755289600