Triple and reverse digits.

Terms

a(0) =1a(1) =3a(2) =9a(3) =72a(4) =612a(5) =6381a(6) =34191a(7) =375201a(8) =3065211a(9) =3365919a(10) =75779001a(11) =300733722a(12) =661102209a(13) =7266033891a(14) =37610189712a(15) =631965038211