a(n) = A289677(3*n).

Terms

a(0) =1a(1) =3a(2) =5a(3) =13a(4) =20a(5) =44a(6) =89a(7) =192a(8) =396a(9) =814a(10) =1610a(11) =3130a(12) =6103a(13) =12229a(14) =24736a(15) =49879a(16) =100747a(17) =203765a(18) =411403