a(n) = 2*a(n-1) + 9*a(n-2), with a(0) = 0, a(1) = 1.

Terms

a(0) =0a(1) =1a(2) =2a(3) =13a(4) =44a(5) =205a(6) =806a(7) =3457a(8) =14168a(9) =59449a(10) =246410a(11) =1027861a(12) =4273412a(13) =17797573a(14) =74055854a(15) =308289865a(16) =1283082416a(17) =5340773617a(18) =22229288978a(19) =92525540509a(20) =385114681820