This is the number of positions that can be reached in n moves from the start, but which cannot be reached in fewer than n moves.
A puzzle in the Rubik cube family. The total number of distinct positions is 2520.
Table of n, a(n) for n=0..9.
Jaap Scherphuis, Puzzle Pages
Sequence in context: A180224 A293005 A173412 * A115390 A005056 A014143
Adjacent sequences: A079815 A079816 A079817 * A079819 A079820 A079821
N. J. A. Sloane, Feb 20 2003