Coordination Sequences and Critical Points
  Coordination sequences of periodic and quasiperiodic graphs are analysed. These count the number of points that can be reached from a given point of the graph by a number of steps along its bonds, thus generalising the familiar coordination number which is just the first member of this series. A possible application to the theory of critical phenomena in lattice models is outlined. 
Michael Baake, Uwe Grimm, Przemyslaw Repetowicz, Dieter Joseph