a(n) = 6*a(n-1)-8*a(n-2) for n>1, a(0)=1, a(1)=9.

Terms

a(0) =1a(1) =9a(2) =46a(3) =204a(4) =856a(5) =3504a(6) =14176a(7) =57024a(8) =228736a(9) =916224a(10) =3667456a(11) =14674944a(12) =58710016a(13) =234860544a(14) =939483136a(15) =3758014464a(16) =15032221696a(17) =60129214464a(18) =240517513216a(19) =962071363584