References to A054731

Numbers of the form x*(x + 1)*y*(y + 1)/4 where x and y are distinct.
0, 3, 6, 10, 15, 18, 21, 28, 30, 36, 45, 55, 60, 63, 66, 78, 84, 90, 91, 105, 108, 120

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