Power of three
In mathematics, a power of three is a number of the form 3n where n is an integer, that is, the result of exponentiation with number three as the base and integer n as the exponent. The first ten non-negative powers of three are:
1, 3, 9, 27, 81, 243, 729, 2187, 6561, 19683, etc. (sequence A000244 in OEIS)