Sequence of Powers of 9

Integer Sequence
The sequence of powers of $9$ begins:
 * $1, 9, 81, 729, 6561, 59 \, 049, 531 \, 441, 4 \, 782 \, 969, 43 \, 046 \, 721, 387 \, 420 \, 489, \ldots$