〈a, b | aba=b, aaaa=aa〉

Properties

• Infinite commutative monoid
• Isomorphic to commutative presentation: 〈a, b | a+2b=a, 4b=2b〉
• Grothendieck group is ℤ₂ ⊕ ℤ

Completion parameters

• Reduction order: left-to-right ab

Complete rewriting system

1. ba ⇒ ab
2. a²b ⇒ b
3. a⁴ ⇒ a²

Right Cayley graph (truncated)