a(n) = floor(((1+sqrt(3))/2)^n).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =8a(7) =12a(8) =16a(9) =22a(10) =30a(11) =42a(12) =57a(13) =78a(14) =107a(15) =147a(16) =200a(17) =274a(18) =374a(19) =511a(20) =699a(21) =955a(22) =1304a(23) =1782a(24) =2434a(25) =3326a(26) =4543a(27) =6206a(28) =8478a(29) =11581