This graph gained graph-theorists recognition
for it seems to fail many general properties.
It is often advised that one should always check any new conjecture
about graphs first against Petersen's graph before an attempt
to prove it.
Click on the figure to see two forms of the graph.
Julius Petersen (1839--1910, Denmark) wrote in 1891 a paper on regular graphs and coloring from which the Petersen's graph comes from. He also did research in algebra, number theory, analysis and mechanic. Remembered in Denmark as a great teacher.
The harmonic evolution digraph consists of 16 pretty "bushy" trees:
| Loops | = | 16 L1 | |
| Tree | = | T14 * T2 |