The longhorn graph is the graph on 7 vertices illustrated above.
It is implemented in the Wolfram Language as GraphData["LonghornGraph"].
Longhorn Graph
See also
A Graph, Bull GraphExplore with Wolfram|Alpha
References
ISGCI: Information System on Graph Class Inclusions v2.0. "List of Small Graphs." http://www.graphclasses.org/smallgraphs.html.Cite this as:
Weisstein, Eric W. "Longhorn Graph." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/LonghornGraph.html