〈a, b | aaaa=a, babab=a〉

Properties

• Infinite commutative monoid
• Isomorphic to commutative presentation: 〈a, b | 4b=b, 3a+b=3b〉
• Grothendieck group is ℤ₉

Completion parameters

• Reduction order: left-to-right ab

Complete rewriting system

1. ba ⇒ ab
2. a⁴ ⇒ a
3. ab³ ⇒ a³

Right Cayley graph (truncated)