i have received this math riddle which i cannot solve,
the riddle:
given a set of cubes, a unique shape is any shape that was created joining cubes sides together and does not match any previously created shapes.
for example
- if we have a set of 2 cubes there is only 1 unique shape (2 cubes connected)
- given a set of 3 cubes there is only 2 unique shapes (L shape and straight line)
- with 4 cubes there are 8 unique shapes,
[you must use all cubes in shape]
what is the number of unique shapes for an N cube set ?