The multiplicity function ( MF ) of groups and clusters of galaxies is determined using galaxy catalogues extracted from a set of Digitized Palomar Sky Survey ( DPOSS ) plates .
The two different types of structures ( of low and high richness ) were identified using two different algorithms : a modified version of the van Albada method for groups , and a peak finding algorithm for larger structures .
In a 300 deg ^ { 2 } area up to z < 0.2 , we find 2944 groups and 179 clusters .
Our MF covers a wide range of richnesses , from 2 to 200 , and the two MF ’ s derived by the two algorithms match smoothly without the need for additional conditions or normalisations .
The resulting multiplicity function , of slope \alpha = -2.08 \pm 0.07 , strongly resembles a power law .