a(1) = 1, then A007051 ((3^n)+1)/2 interleaved with A057198 (5*3^(n-1)+1)/2.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =8a(5) =14a(6) =23a(7) =41a(8) =68a(9) =122a(10) =203a(11) =365a(12) =608a(13) =1094a(14) =1823a(15) =3281a(16) =5468a(17) =9842a(18) =16403a(19) =29525a(20) =49208a(21) =88574a(22) =147623a(23) =265721a(24) =442868a(25) =797162a(26) =1328603a(27) =2391485a(28) =3985808a(29) =7174454