A trisection of A163129.

Terms

a(0) =3a(1) =75a(2) =969a(3) =8964a(4) =66975a(5) =429096a(6) =2442372a(7) =12640320a(8) =60454713a(9) =270391857a(10) =1141260315a(11) =4578160257a(12) =17554638039a(13) =64642406670a(14) =229486544439a(15) =788018124312