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

Terms

a(0) =1a(1) =5a(2) =23a(3) =105a(4) =479a(5) =2185a(6) =9967a(7) =45465a(8) =207391a(9) =946025a(10) =4315343a(11) =19684665a(12) =89792639a(13) =409593865a(14) =1868384047a(15) =8522732505a(16) =38876894431a(17) =177339007145a(18) =808941246863