Orthogonal Array

An orthogonal array OA$(k,s)$ is a $k\times s^2$ Array with entries taken from an $s$-set $S$ having the property that in any two rows, each ordered pair of symbols from $S$ occurs exactly once.

References

Colbourn, C. J. and Dinitz, J. H. (Eds.) CRC Handbook of Combinatorial Designs. Boca Raton, FL: CRC Press, p. 111, 1996.