Furthermore, a Patterson map of N points will have N(N − 1) peaks, excluding the central (origin) peak and any overlap.
The peaks' positions in the Patterson function are the interatomic distance vectors and the peak heights are proportional to the product of the number of electrons in the atoms concerned.
Because for each vector between atoms i and j there is an oppositely oriented vector of the same length (between atoms j and i), the Patterson function always has centrosymmetry.
^Patterson, A. L. (1935). "A direct method for the determination of the components of interatomic distances in crystals". Zeitschrift für Kristallographie. 90 (1–6): 517. doi:10.1524/zkri.1935.90.1.517. S2CID102041995.