The 5th/6th term may be considered as II0I in base 27, analogizing with the hexadecimal system. The 4th term is 2112 in base 13, (42)(42) in base 103, and AI in base 456. (In base-ten terms.)
Table of n, a(n) for n=1..8.
Sequence in context: A319456 A222713 A138959 * A055435 A242868 A070418
Adjacent sequences: A171650 A171651 A171652 * A171654 A171655 A171656
James G. Merickel, Dec 14 2009
Seventh term added by James G. Merickel, Feb 03 2010
Eighth term added by James G. Merickel, Feb 12 2010