a(n) = 2*a(n-1) + 9*a(n-2), with a(0)=a(1)=1.

Terms

a(0) =1a(1) =1a(2) =11a(3) =31a(4) =161a(5) =601a(6) =2651a(7) =10711a(8) =45281a(9) =186961a(10) =781451a(11) =3245551a(12) =13524161a(13) =56258281a(14) =234234011a(15) =974792551a(16) =4057691201a(17) =16888515361a(18) =70296251531a(19) =292589141311