Simplify level-cycle search table

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2026-06-01 13:33:29 -04:00
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@@ -1345,6 +1345,35 @@ $S \subseteq V(G)$ such that $G$ admits a proper $4$-vertex-colouring
with the level-cycle three-colour restriction with respect to $S$.
\end{conjecture}
\subsection*{Enumeration for small $n$}
We exhaustively enumerated all plane triangulation isomorphism classes with
$4 \leq n \leq 12$ vertices and, for each graph, searched the vertex sources
in order until a witness colouring was found or every source had been tested.
No counterexample to Conjecture~\ref{conj:level-cycle-three-colour} appeared
in this range. Table~\ref{tab:level-cycle-three-colour-counts} records the
size of the search space and the amount of source-search work required.
\begin{table}[ht]
\centering
\small
\setlength{\tabcolsep}{4pt}
\begin{tabular}{cccc}
$n$ & triangulations & with witness & source checks \\\hline
$4$ & $1$ & $1$ & $1$ \\
$5$ & $1$ & $1$ & $1$ \\
$6$ & $2$ & $2$ & $2$ \\
$7$ & $5$ & $5$ & $5$ \\
$8$ & $14$ & $14$ & $14$ \\
$9$ & $50$ & $50$ & $50$ \\
$10$ & $233$ & $233$ & $237$ \\
$11$ & $1249$ & $1249$ & $1296$ \\
$12$ & $7595$ & $7595$ & $8069$ \\
\end{tabular}
\caption{Exhaustive vertex-source search for the level-cycle three-colour conjecture on all triangulation isomorphism classes with $4 \leq n \leq 12$. Every triangulation in this range admits at least one vertex source witnessing the conjecture.}
\label{tab:level-cycle-three-colour-counts}
\end{table}
\begin{definition}[Seam]
\label{def:seam}
A \emph{seam} of a maximal planar graph $G$ is a simple cycle