Double the number plants than square system of planting can be accommodated in which other planting system?

Double the number of plants than a square system of planting can be accommodated in both Cluster system and Quincunx system of planting.
Quincunx system is the square method but with one more plant in the centre of the square. This will accommodate double the number of plants, but does not provide equal spacing.
In cluster systems planting a plant, the cluster was defined as being an individual plant or a tightly clumped group of individual plants.