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The reciprocal of $e^{-x}$ has a power series about $0$ in which all coefficients are non-negative. Gessel [Reciprocals of exponential polynomials and permutation enumeration, Australas. J. Combin., 74, 2019] considered truncates of the power series
Externí odkaz:
http://arxiv.org/abs/2303.14057
Akademický článek
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Autor:
Engbers, John, Erey, Aysel
Publikováno v:
In Discrete Applied Mathematics 31 December 2023 341:308-321
Let $P_G(k)$ be the number of proper $k$-colorings of a finite simple graph $G$. Tomescu's conjecture, which was recently solved by Fox, He, and Manners, states that $P_G(k) \le k!(k-1)^{n-k}$ for all connected graphs $G$ on $n$ vertices with chromat
Externí odkaz:
http://arxiv.org/abs/1912.03236
Worpitzky's identity expresses $n^p$ in terms of the Eulerian numbers and binomial coefficients: $$n^p = \sum_{i=0}^{p-1} \genfrac<>{0pt}{}{p}{i} \binom{n+i}{p}.$$ Pita-Ruiz recently defined numbers $A_{a,b,r}(p,i)$ implicitly to satisfy a generalize
Externí odkaz:
http://arxiv.org/abs/1910.02977
We study the problem of maximizing the number of independent sets in $n$-vertex $k$-chromatic $\ell$-connected graphs. First we consider maximizing the total number of independent sets in such graphs with $n$ sufficiently large, and for this problem
Externí odkaz:
http://arxiv.org/abs/1907.03913
Autor:
Engbers, John, Stocker, Christopher
We classify the trees on $n$ vertices with the maximum and the minimum number of certain generalized colorings, including conflict-free, odd, non-monochromatic, star, and star rainbow vertex colorings. We also extend a result of Cutler and Radcliffe
Externí odkaz:
http://arxiv.org/abs/1707.03910
Autor:
Engbers, John
Publikováno v:
Graphs & Combinatorics; Dec2024, Vol. 40 Issue 6, p1-14, 14p
Given $R \subseteq \mathbb{N}$ let ${n \brace k}_R$, ${n \brack k}_R$, and $L(n,k)_R$ be the number of ways of partitioning the set $[n]$ into $k$ non-empty subsets, cycles and lists, respectively, with each block having cardinality in $R$. We refer
Externí odkaz:
http://arxiv.org/abs/1610.05803
Autor:
Engbers, John
For graphs $G$ and $H$, an $H$-coloring of $G$ is a map from the vertices of $G$ to the vertices of $H$ that preserves edge adjacency. We consider the following extremal enumerative question: for a given $H$, which connected $n$-vertex graph with min
Externí odkaz:
http://arxiv.org/abs/1601.05040