A victim is robbed late at night on public street.  The defendant flees in a vehicle.  A homeless person sees the entire robbery and immediately writes down the license plate of the defendant's vehicle on the back of a cigarette carton.  The homeless person states that he can remember the license plate number from his own memory.  The prosecutor seeks to admit the writing on the cigarette carton into evidence.  The defense lawyer objects.

Is this hearsay? Why or why not?