Schmeichel–Hakimi conjecture on exceptional planar graphical sequences
A graphical sequence is planar graphical if it is the degree sequence of a planar graph. Using the shorthand for repetitions of followed by repetitions of , consider the sequences , , and . Schmeichel–Hakimi conjecture. None of these three sequences is planar graphical. The source states that these are the three unresolved cases remaining after their theorem, so the conjecture is open.
References
Primary source
Jorik Jooken, “Computer-assisted graph theory: a survey”, arXiv:2508.20825 (2025).
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