Questions tagged [latin-square]

For questions on or pertaining to Latin squares.

In combinatorics and in experimental design, a Latin square is an $n \times n$ array filled with $n$ different symbols, each occurring exactly once in each row and exactly once in each column.

For example, the two Latin squares of order two are given by $$\begin{pmatrix} 1 & 2 \\ 2 & 1 \end{pmatrix}\qquad\text{and}\qquad\begin{pmatrix} 2 & 1 \\ 1 & 2 \end{pmatrix}$$

  • Sudoku is a special case of a Latin square.
  • In the design of experiments, Latin squares are a special case of row-column designs for two blocking factors.
  • Many row-column designs are constructed by concatenating Latin squares.
  • In algebra, Latin squares are generalizations of groups.
  • In fact, Latin squares are characterized as being the multiplication tables (Cayley tables) of quasigroups.
  • A binary operation whose table of values forms a Latin square is said to obey the Latin square property.

References:

https://en.wikipedia.org/wiki/Latin_square#Applications

http://mathworld.wolfram.com/LatinSquare.html

225 questions
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symmetric latin square of order 5

My textbook said if a latin square of order 5 is idempotent and had a 2 in the (1,3) entry, it could not be completed as a symmetric square. But isn't this one such square? Or do I have the definition of "symmetric" wrong? 1 4 2 5 3 4 2 …
user81055
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Art hobbyist seeking maximally dispersed Latin Square of order 7

I'm an art hobbyist working on a painting that has a grid of $7$ rows and columns with a painted rectangle (rounded corners) at each grid position. I wanted to use $7$ colours and not have a colour repeat in any row or column. Googling I found this…
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What does a non-mathematician need to google to learn more about latin squares in which each number in each row always has a different successor?

First off, my apologies for the long and convoluted title. I am no mathematician so I don't know the "proper" terms to use... which is exactly my problem: I want to find a/any/one Latin square of order 8 in which each pair of numbers in each row…
hcc23
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Modified latin square

I'm trying to build a variation of a latin square. In a latin square of size $n$, every row and every column contains a number from $1$ to $n$ exactly once. Given arbitrary $a$ and $b$ such that $n=a\cdot b$, I would like to build a size $n$ square…
bprs
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Double Latin squares

I was messing around with a mostly-unrelated crypto problem, and I encountered this puzzle: Let's define a "double Latin square": 1) It uses two-digit numbers, that start with 1-n, and also have a second digit in the range 1-n. (For example: 11, 12,…
blake8086
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Quadrangle criterion for a matrix

I need help understanding the quadrangle criterion. First of all, I find it very hard to find anything related to it. The only two things I came up with are these: "Reconstruction of Multiplication Tables" by P. Vojtechovsky and "On Minimum…
nSeidel
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How many structurally distinct Latin squares are there of order 7?

What is the 7th term of https://oeis.org/A264603? A264603 Number of structurally distinct Latin squares of order n. "Structurally distinct" means that the squares cannot be made identical by means of rotation, reflection, and/or permutation of the…
Claude
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Rank-reducibility of Latin squares

Consider the following Latin square with rank $N= 9$: $$ \begin{bmatrix} 5 & 3 & 1 & 2 & 4 & 7 & 6 & 8 & 9 \\ 3 & 7 & 9 & 6 & 8 & 4 & 5 & 2 & 1 \\ 8 & 5 & 4 & 9 & 1 & 2 & 7 & 3 & 6 \\ 9 & 2 & 3 & 8 & 7 & 6 & 1 & 4 & 5 \\ 7 & 4 & 5 & 3 & 9…
Jim White
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Need help understanding a proof about $N_{2}$ latin squares.

I understand what the author is doing in Theorem 1.3.1 intercalate proof, however I don't see how this proof relies on the fact that $n$ needs to be odd. It seems to me the same logic holds for any $n$ (though, I do know there are latin square…
brt
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Can someone clarify the definition for two Latin squares to be orthogonal for me please?

I have been given this definition for two Latin Sqaures to be orthogonal. Let $L, M$ be two $n\times n$ Latin squares with entries taken from the sets $X = \{x_1, x_2,\dots, x_n\}$,$\ \ Y = \{y_1, y_2,\dots, y_n\}$ respectively and $(n > 1)$. Then…
Jed
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Producing a Latin Square given the first two rows

I generally have a decent understanding of Latin Squares, at least I think I do, and I'm just running through some practice questions but I've found one that has puzzled me. When constructing Latin Squares I understand that we only want each symbol…
Sean E.
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Check my proof on Latin Squares

Define a set of $n - 1$ mutually orthogonal squares $A_1, \ldots, A_{n-1}$, where n is a prime number. If we set the element $(i, j)$ in square $A_h$ as $i + hj$ then the squares in the set are mutually orthogonal squares. (1) each square is a Latin…
user81055
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Is a $4×4$ Latin square possible whose trace-sum is 7 or 9 or 13 or 15?

A Latin square with trace-sum $11$ is : $$\begin{bmatrix} 1&4&2&3\\ 2&3&4&1\\ 4&1&3&2\\ 3&2&1&4\end{bmatrix}$$ Is trace sum $7/9/5/13/15$ possible in some other arrangement?
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Equivalence between Latin squares

I have two Latin squares of order 6. Is there any way to check whether they are isomorphic? I mean any program or online tool? $ L_1= \left[ {\begin{array}{cccccc} 1 & 2 & 3 & 4 & 5 & 6\\ 2 & 4 & 5 & 1 & 6 & 3 \\ 3 & 1 & 2 & 6 & 4 & 5\\ …
budi
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Application of Latin Squares

There are 36 officers, six officers of six different ranks in each of 6 regiments. Find an arrangement of the 36 officers in a $6\times 6$ square formation such that each row and each column contains one and only one officer from each regiment of…
NANI
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