## (2,1) de Bruijn diagrams

The parameters governing the shift-period de Bruijn diagrams are the number of generations involved and the shifting required; there are usually enough letters in the alphabet to assign each combination a unique letter. An exception is the case of binary automata with first neighbors. The layout in Table 1 shows how to specify combinations of period and shift.

Table 1:Binary de Bruijn menu layout.

First type a letter in the range

atom, for a shift lying between 6 cells to the left and 6 cells to the right. Then type a second letter in the rangeatog, for the periodicity. Thus,gawill yield still lifes,chdesigns which shift right one cell every three generations, and so on.The combinations marked with a

.are superluminal patterns, the remainder travel at the velocity of light or less, and are marked by+.

Harold V. McIntosh

E-mail:mcintosh@servidor.unam.mx