# Regular expression for all a* except aa?

I'm stumped on how you would describe a language which is a* except for aa, so the following is acceptable:

a
aaa
aaaa
aaaaa
...


It's for part of the below DFA

Hint: A word consisting of $$n \neq 2$$ many $$a$$s either consists of zero $$a$$s, or of a single $$a$$, or of at least three many $$a$$s.