Begin with a finite sequence of blocks in a row, each in one of 3 colors: red, blue, yellow.

Below each pair of neighboring blocks place a new block with the color rule: If the blocks are the same color use that color but if they are different use the third color.

Example:

r b y y b
 y r y r
  b b b
   b b
    b

How can the color of the last block be easily predicted from the top row?

Note: I don't know the full answer but can solve special cases.

(In reply to proposed solution by xdog)

I think you got it.  I didn't think working with numbers would work because 0+1=2, 0+2=1, 2+1=0 isn't recognizeable.  

Posted by Jer on 2018-12-18 11:07:19