References to A154638

a(n) is the number of unique reduced words of length n (i.e. all possible length-reducing cancellations have been applied and words that are equal are counted only once) in the Coxeter group of "Apollonian reflections" in three dimensions. This group has five generators, satisfying (S_i)^2 = (S_i S_j)^3 = I.
1, 5, 20, 70, 240, 810, 2730, 9180, 30870, 103770, 348840, 1172610, 3941730

1 seqfan posts

Sun Nov 22 04:11:09 CET 2009    [seqfan] No. of words of length n in certain group

Index of A-numbers in seqfan: by ascending order    by month    by frequency    by keyword
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