The history of the discovery, and significance, of the Rotas square has been documented in detail in Word Ways, particularly by Dmitri A. Borgmann (WW November 1979 page 195.). I do not intend to delve into that aspect of the square here.
"The Rotas Square - A Numerical Challenge,"
Word Ways: Vol. 46
, Article 5.
Available at: http://digitalcommons.butler.edu/wordways/vol46/iss3/5