# Non-repeating patterns

There are 243 non-repeating patterns.
These can be conveniently divided into four further groups.
The first group are those which have a distinct spiral structure.
An example of such a pattern is:
The second group are those tilings of a rectangle by polyominoes,
and example of which is:
The third group are those tilings of a square into similar triangles,
and example of which is:
The other group has no such spiral structure - an example
of which is:
Now you must choose:
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