The number of transversals in a Latin square.

Autor: Brendan McKay, Jeanette McLeod, Ian Wanless
Zdroj: Designs, Codes & Cryptography; Sep2006, Vol. 40 Issue 3, p269-284, 16p
Abstrakt: Abstract  A Latin Square of order n is an n ×  n array of n symbols, in which each symbol occurs exactly once in each row and column. A transversal is a set of n entries, one selected from each row and each column of a Latin Square of order n such that no two entries contain the same symbol. Define T(n) to be the maximum number of transversals over all Latin squares of order n. We show that $$b^n \leq T(n) \leq c^n\sqrt{n}\,n!$$ for n ≥ 5, where b ≈ 1.719 and c ≈ 0.614. A corollary of this result is an upper bound on the number of placements of n non-attacking queens on an n ×  n toroidal chess board. Some divisibility properties of the number of transversals in Latin squares based on finite groups are established. We also provide data from a computer enumeration of transversals in all Latin Squares of order at most 9, all groups of order at most 23 and all possible turn-squares of order 14. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index