a(n) = 3*a(n-1) + 10*a(n-2).

Terms

a(0) =0a(1) =1a(2) =3a(3) =19a(4) =87a(5) =451a(6) =2223a(7) =11179a(8) =55767a(9) =279091a(10) =1394943a(11) =6975739a(12) =34876647a(13) =174387331a(14) =871928463a(15) =4359658699a(16) =21798260727a(17) =108991369171a(18) =544956714783