Let $E$ be the set of even integers and let $O$ be the set of odd integers. Suppose that a computer is programmed to input a sequence of elements of $E$ and output a sequence of elements of $O$ according to some rule. You run a test of this program using $12, 6, 8, 10, 2$ as input, and the computer outputs $81, 9, 25, 49, 1$. What rule does the computer appear to be using?