<a href="https://en.wikipedia.org/wiki/Kissing_number" class="extiw" title="w:Kissing number">Kissing number</a> in one dimension is 2
<a href="//commons.wikimedia.org/wiki/User:N.Mori" title="User:N.Mori">N.Mori</a>
2007-02-27
<a href="//commons.wikimedia.org/wiki/File:Kissing-1d.jpg" class="image"><img alt="Kissing-1d.jpg" src="https://upload.wikimedia.org/wikipedia/commons/5/53/Kissing-1d.jpg" decoding="async" width="182" height="35" data-file-width="182" data-file-height="35"></a>