Age 14 to 16
The Frieze Symmetries are an important mathematical idea.
The question is about an infinite sequence of translations mapping
onto itself by :
Reflection, V (vertical mirror line)
or Reflection, H (horizontal mirror line)
or Rotation, R
or by a combination of H with a half unit shift left or right (G,
glide reflection) .
This is an excellent opportunity for children to categorize : R or
not R, V or not V, etc.
There are in fact only 7 categories, and there's plenty to explore
and discuss as the combination options are investigated.