That is, count a 180° move as two 90° moves. Which it is, though we usually don't think of it that way.
Assuming a random move length distribution, that would only leave a (2/3)^20 fraction of them, which is about 147000 positions.
https://www.cube20.org/qtm/
That is, count a 180° move as two 90° moves. Which it is, though we usually don't think of it that way.
Assuming a random move length distribution, that would only leave a (2/3)^20 fraction of them, which is about 147000 positions.