A remark on the counterexample to the unknotting number conjecture

Chao Wang, Yimu Zhang

By using Snappy, M. Brittenham and S. Hermiller discovered a very surprising example that $u(7_1\#\overline{7_1})\le 5<6=u(7_1)+u(\overline{7_1})$, where $7_1$ is the $(2,7)$-toru…