a(n) = 5*a(n-1) - a(n-2), with a(0) = 1 and a(1) = 2.

Terms

a(0) =1a(1) =2a(2) =9a(3) =43a(4) =206a(5) =987a(6) =4729a(7) =22658a(8) =108561a(9) =520147a(10) =2492174a(11) =11940723a(12) =57211441a(13) =274116482a(14) =1313370969a(15) =6292738363a(16) =30150320846a(17) =144458865867a(18) =692144008489