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math.CO2021
ZZ Polynomials of Regular -tier Benzenoid Strips as Extended Strict Order Polynomials of Associated Posets -- Part 1. Proof of Equivalence
Johanna Langner, Henryk A. Witek
In Part 1 of the current series of papers, we demonstrate the equivalence between the Zhang-Zhang polynomial of a Kekuléan regular -tier strip $\bo…
math.CO2020
Zhang-Zhang Polynomials of Ribbons
Bing-Hau He, Chien-Pin Chou, Johanna Langner +1
We report a closed-form formula for the Zhang-Zhang polynomial (aka ZZ polynomial or Clar covering polynomial) of an important class of elementary pericondensed benzenoids $Rb\left…
math.CO2020
In how many distinct ways can flocks be formed? A problem in sheep combinatorics
Johanna Langner, Henryk A. Witek
In this short paper, we extend the concept of the strict order polynomial , which enumerates the number of strict order-preserving maps $ϕ:P\rightarrow\boldsymbol…