He sends an e-mail to 3 of his friends (call this round 1).
Each of these friends forwards the e-mail to 3 other people (round 2).
Those 9 people each forward the e-mail to 3 other people (round 3), and so on.
Assume that nobody receives the e-mail more than once.
Determine an expression for the total number of people, including Elijah, who are aware of the good news by the nth round.