〈a, b | ba=ab, aaa=aa〉

Properties

• Infinite commutative monoid
• Isomorphic to commutative presentation: 〈a, b | 3b=2b〉
• Grothendieck group is ℤ

Completion parameters

• Reduction order: left-to-right ab

Complete rewriting system

1. ba ⇒ ab
2. a³ ⇒ a²

Right Cayley graph (truncated)