I've been looking at this problem for ages and still can't work out what to do so help would be much appreciated!

Problem:

Set A is defined recursively. Find four elements in Set A.

2 ∈ A

x, y ∈ A, then x*y ∈ A (multiplication)

[I thought a clause may have been missing, but not entirely sure.. recursion isn't a strong point of mine..]

Thanks!