a(n) = Product_{d|n, d<n} A019565(d)^[2 == d mod 3].

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =1a(5) =3a(6) =1a(7) =3a(8) =1a(9) =30a(10) =1a(11) =3a(12) =1a(13) =3a(14) =10a(15) =21a(16) =1a(17) =3a(18) =1a(19) =30a(20) =1a(21) =126a(22) =1a(23) =21a(24) =10a(25) =3a(26) =1a(27) =315a(28) =1a(29) =30