The Dinitz problem solved for rectangles

How many latin rectangles are there?

Until now the problem counting Latin rectangles m x n has been solved with an explicit formula for m = 2, 3 and 4 only. In the present paper an explicit formula is provided for the calculation of the number of Latin rectangles for any order m. The results attained up to now become particular cases of this new formula. Furthermore, putting m = n, the number of Latin squares of order n can also be obtained in an explicit form.

Ryser's Theorem for $ρ$-latin Rectangles

Let $L$ be an $n\times n$ array whose top left $r\times s$ subarray is filled with $k$ different symbols, each occurring at most once in each row and at most once in each column. We find necessary and sufficient conditions that ensure the remaining cells of $L$ can be filled such that each symbol occurs at most once in each row and at most once in each column, and each symbol occurs a prescribed number of times in $L$. The case where the prescribed number of times each symbol occurs is $n$ was solved by Ryser (Proc. Amer. Math. Soc. 2 (1951), 550--552), and the case $s=n$ was settled by Goldwa…

将4 by n网格切成两块全等部分

Cutting 4 by $n$ grids into two congruent pieces

本文用传递矩阵法解决将4 by n矩形分成两块全等部分的问题，并计算生成函数。

平衡的斐波那契词矩形，以及更广泛的领域

Balanced Fibonacci word rectangles, and beyond

本文基于Anselmo等人近期的研究，探讨了由斐波那契词构成的m×n矩形矩阵的平衡性质，并通过有限自动机解决，进一步推广到所有二次无理数对应的Sturmian特征词，还研究了 tribonacci 词和Thue-Morse 词的类似问题。

Graphical Enumeration and Stained Glass Windows, 1: Rectangular Grids

A survey of enumeration problems arising from the study of graphs formed when the edges of a polygon are marked with evenly spaced points and every pair of points is joined by a line. A few of these problems have been solved, a classical example being the the graph K_n formed when all pairs of vertices of a regular n-gon are joined by chords, which was analyzed by Poonen and Rubinstein in 1998. Most of these problems are unsolved, however, and this two-part article provides data from a number of such problems as well as colored illustrations, which are often reminiscent of stained glass window…

Intensive use of computing resources for dominations in grids and other combinatorial problems

Our goal is to prove new results in graph theory and combinatorics thanks to the speed of computers, used with smart algorithms. We tackle four problems. The four-colour theorem states that any map whose countries are connected can be coloured with 4 colours such that neighbouring countries have differnt colours. It was the first result proved using computers, in 1989. We wished to automatise further its proof. We explain the proof and provide a program which replays the proof. It also makes it possible to obtain other results with the same method. We give ideas to automatise the search for di…