a(n) = 3*a(n-1) + 5*a(n-2), with a(0)=0, a(1)=1.

Terms

a(0) =0a(1) =1a(2) =3a(3) =14a(4) =57a(5) =241a(6) =1008a(7) =4229a(8) =17727a(9) =74326a(10) =311613a(11) =1306469a(12) =5477472a(13) =22964761a(14) =96281643a(15) =403668734a(16) =1692414417a(17) =7095586921a(18) =29748832848a(19) =124724433149a(20) =522917463687