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

Terms

a(0) =1a(1) =7a(2) =55a(3) =433a(4) =3409a(5) =26839a(6) =211303a(7) =1663585a(8) =13097377a(9) =103115431a(10) =811826071a(11) =6391493137a(12) =50320119025a(13) =396169459063