Powers of 3 written in base 4.

Terms

a(0) =1a(1) =3a(2) =21a(3) =123a(4) =1101a(5) =3303a(6) =23121a(7) =202023a(8) =1212201a(9) =10303203a(10) =32122221a(11) =223033323a(12) =2001233301a(13) =12011033103a(14) =102033231321a(15) =312233021223