Frieze Pattern

$$\matrix{& b & \cr a & & d\cr & c & \cr}$$

An arrangement of numbers at the intersection of two sets of perpendicular diagonals such that $a+d=b+c+1$ (for an additive frieze pattern) or $ad=bc+1$ (for a multiplicative frieze pattern) in each diamond.

References

Conway, J. H. and Coxeter, H. S. M. ``Triangulated Polygons and Frieze Patterns.'' Math. Gaz. 57, 87-94, 1973.

Conway, J. H. and Guy, R. K. In The Book of Numbers. New York: Springer-Verlag, pp. 74-76 and 96-97, 1996.