A trisection of A163129.

Terms

a(0) =9a(1) =180a(2) =2070a(3) =17775a(4) =125865a(5) =773766a(6) =4260645a(7) =21453975a(8) =100250100a(9) =439479198a(10) =1822654251a(11) =7198716870a(12) =27221451885a(13) =98988000120a(14) =347428124352