a(n) = 9^n mod 6^n.

Terms

a(0) =0a(1) =3a(2) =9a(3) =81a(4) =81a(5) =4617a(6) =18225a(7) =24057a(8) =1056321a(9) =4468041a(10) =40212369a(11) =180512793a(12) =1624615137a(13) =8091189225a(14) =72820703025a(15) =420293834937