Chess Opening Theory/1. e4/1...c5/2. a3/2...Nc6
The most common and logical move in the situation is 3. b4. With this sacrificial idea white tries to make total control of the center and both the a- and b-files. If black accepts the sacrifice a standard follow-up is: 3...cxb4 4. axb4 Nxb4 5. d4 d5 6. c3 Nc6 7. exd5 Qxd5 8. Na3.
Other moves as Bb5 and Bc4 are standard moves in the Sicilian, where white simply develops a piece and gets a usual Silician situation.