Example 1.1.8.9. For $0 \leq i \leq n$, the horn $\Lambda ^{n}_{i}$ of Construction 1.1.2.9 is given by $\Delta ^{n}_{\operatorname{\mathcal{U}}}$, where $\operatorname{\mathcal{U}}$ is the collection of all nonempty subsets of $[n]$ which are distinct from $[n]$ and $[n] \setminus \{ i \} $.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$