a(n) = 5*a(n-1) - a(n-2).

Terms

a(0) =1a(1) =3a(2) =14a(3) =67a(4) =321a(5) =1538a(6) =7369a(7) =35307a(8) =169166a(9) =810523a(10) =3883449a(11) =18606722a(12) =89150161a(13) =427144083a(14) =2046570254a(15) =9805707187a(16) =46981965681a(17) =225104121218