OFFSET
0,2
COMMENTS
ABA and BAB are equal, but are counted as distinct reduced words.
LINKS
R. L. Graham, J. C. Lagarias, C. L. Mallows, Allan Wilks and C. Yan, Apollonian Circle Packings: Geometry and Group Theory III. Higher Dimensions., Discrete & Computational Geometry, 35 (2006), no. 1, 37-72.
C. L. Mallows, Growing Apollonian Packings, J. Integer Sequences, 12 (2009), article 09.2.1.
EXAMPLE
All 80 squarefree words of length 3 are counted, so a(3) = 80.
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Colin Mallows, Jan 13 2009
STATUS
approved