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

Terms

a(0) =2a(1) =3a(2) =11a(3) =36a(4) =119a(5) =393a(6) =1298a(7) =4287a(8) =14159a(9) =46764a(10) =154451a(11) =510117a(12) =1684802a(13) =5564523a(14) =18378371a(15) =60699636a(16) =200477279a(17) =662131473a(18) =2186871698a(19) =7222746567a(20) =23855111399a(21) =78788080764a(22) =260219353691a(23) =859446141837