a(n) = A289676(3*n+2).

Terms

a(0) =1a(1) =2a(2) =4a(3) =4a(4) =13a(5) =18a(6) =40a(7) =71a(8) =132a(9) =231a(10) =459a(11) =990a(12) =2114a(13) =4237a(14) =8234a(15) =16054a(16) =31280a(17) =60252a(18) =115810