An <a href="https://en.wikipedia.org/wiki/aperiodic_graph" class="extiw" title="en:aperiodic graph">aperiodic graph</a>. The cycles in this graph have lengths 5, 6, and 9; therefore, there is no <i>k</i> &gt; 1 that divides all cycle lengths.
<a href="https://en.wikipedia.org/wiki/User:David_Eppstein" class="extiw" title="wikipedia:User:David Eppstein">David Eppstein</a> at <a href="https://en.wikipedia.org/wiki/" class="extiw" title="wikipedia:">English Wikipedia</a>
Transferred from <span class="plainlinks"><a class="external text" href="https://en.wikipedia.org">en.wikipedia</a></span> to Commons.