OA131
(Package: DiceDesign) :
A 3D orthogonal array of strength 2
A 3-dimensional linear orthogonal array (OA) of strength 2 with 49 points. The design points are equally spaced into 2 dimensional coordinate planes. However by construction, such OAs satisfy a linear relation, here: x1 + 3*x2 + x3 = 0 (mod 7). As a consequence, the design points are contained in parallel planes orthogonal to (1,3,1). Actually, they are also contained in parallel planes orthogonal to other directions, as (2,-1,2) or (3,2,3), since the congruence relation leads to 2*x1 - x2 + 2*x3 = 0 (mod 7) or 3*x1 + 2*x2 + 3*x3 = 0 (mod 7). For instance, they are contained in 4 parallel planes orthogonal to (2,-1,2).
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