(9*11^n+1)/5.

Terms

a(0) =2a(1) =20a(2) =218a(3) =2396a(4) =26354a(5) =289892a(6) =3188810a(7) =35076908a(8) =385845986a(9) =4244305844a(10) =46687364282a(11) =513561007100