a(1)=3, a(2)=5, a(n)=3*a(n-1) + 5*a(n-2).

Terms

a(0) =3a(1) =5a(2) =30a(3) =115a(4) =495a(5) =2060a(6) =8655a(7) =36265a(8) =152070a(9) =637535a(10) =2672955a(11) =11206540a(12) =46984395a(13) =196985885a(14) =825879630a(15) =3462568315a(16) =14517103095a(17) =60864150860a(18) =255177968055