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

Terms

a(0) =1a(1) =6a(2) =28a(3) =120a(4) =496a(5) =2016a(6) =8128a(7) =32640a(8) =130816a(9) =523776a(10) =2096128a(11) =8386560a(12) =33550336a(13) =134209536a(14) =536854528a(15) =2147450880a(16) =8589869056a(17) =34359607296a(18) =137438691328a(19) =549755289600