Example 6.4.1.----Latin square design

a1={65 24, 66 20, 65 24, 65 26};
a2={68 21, 63 23, 67 25, 64 25};
a3={67 26, 64 25, 64 19, 64 25};
a4={68 27, 67 24, 63 20, 68 22};