Power of three

For other uses, see Power of Three.
81 (34) combinations of weights of 1 (30), 3 (31), 9 (32) and 27 (33) kg – each weight on the left pan, right pan or unused – allow integer weights from −40 to +40 kg to be balanced; the figure shows the positive values

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.

In base 10, every power of 3 has an even number as its second-last digit.