Chess Opening Theory/1. e4/1...c5/2. a3/2...Nc6

=Mengarini Variation= The most common and logical follow-up to 2. a3 in this situation is 3. b4, a delayed, with the idea to deflect the c5-pawn from the center.

Theory table
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'''1. e4 c5 2. a3 Nc6'''