Powers of 3 written backwards.

Terms

a(0) =1a(1) =3a(2) =9a(3) =72a(4) =18a(5) =342a(6) =927a(7) =7812a(8) =1656a(9) =38691a(10) =94095a(11) =741771a(12) =144135a(13) =3234951a(14) =9692874a(15) =70984341a(16) =12764034a(17) =361041921a(18) =984024783a(19) =7641622611a(20) =1044876843a(21) =30235306401a(22) =90695018313a(23) =72887134149a(24) =184635924282a(25) =344906882748