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

Terms

a(0) =1a(1) =2a(2) =11a(3) =64a(4) =373a(5) =2174a(6) =12671a(7) =73852a(8) =430441a(9) =2508794a(10) =14622323a(11) =85225144a(12) =496728541a(13) =2895146102a(14) =16874148071a(15) =98349742324a(16) =573224305873