〈a, b | aaaa=ab, babb=a〉

Properties

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

Completion parameters

• Reduction order: left-to-right a/b

Complete rewriting system

1. a¹⁰ ⇒ a
2. ba ⇒ a⁴
3. ab ⇒ a⁴

Right Cayley graph (truncated)