a(n) = A289677(3*n+2).

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =19a(5) =46a(6) =88a(7) =185a(8) =380a(9) =793a(10) =1589a(11) =3106a(12) =6078a(13) =12147a(14) =24534a(15) =49482a(16) =99792a(17) =201892a(18) =408478