a(n) = J_9(n)/J_3(n), where J_k is the k-th Jordan totient function.

Terms

a(0) =1a(1) =73a(2) =757a(3) =4672a(4) =15751a(5) =55261a(6) =117993a(7) =299008a(8) =551853a(9) =1149823a(10) =1772893a(11) =3536704a(12) =4829007a(13) =8613489a(14) =11923507a(15) =19136512a(16) =24142483a(17) =40285269a(18) =47052741a(19) =73588672a(20) =89320701a(21) =129421189a(22) =148048057a(23) =226349056a(24) =246109375a(25) =352517511a(26) =402300837a(27) =551263296