ABSTRACT
Among the principal lists, exactly ten have a set of four disjoint elementary pairs. The lists Ln with n = 11, 12, 13, 14, 19, 20, 21, 22 each have disjoint elementary pairs (1ˆ, 8ˆ), (2ˆ, 7ˆ), (3ˆ, 6ˆ), (4ˆ, 5ˆ). Each of the two lists Ln with n = 88, 92 has disjoint elementary pairs (1ˆ, 5ˆ), (2ˆ, 6ˆ), (3ˆ, 7ˆ), (4ˆ, 8ˆ). We explain hereafter how to realize these lists directly.
