a(n) = 5*a(n-1) - 3*a(n-2), a(0)=1, a(1)=6.

Terms

a(0) =1a(1) =6a(2) =27a(3) =117a(4) =504a(5) =2169a(6) =9333a(7) =40158a(8) =172791a(9) =743481a(10) =3199032a(11) =13764717a(12) =59226489a(13) =254838294a(14) =1096512003a(15) =4718045133a(16) =20300689656a(17) =87349312881a(18) =375844495437