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A359705
Cogrowth sequence of the Brin-Navas group B.
2
1, 4, 28, 232, 2092, 19864, 195352, 1970896, 20275692, 211825600, 2240855128, 23952786400, 258287602744, 2806152315048, 30686462795856, 337490492639512, 3730522624066540, 41422293291178872, 461802091590831904, 5167329622166765872
OFFSET
0,2
COMMENTS
This is the number of words of length 2n equal to the identity in the letters t, t^{-1}, a, a^{-1} which generate the Brin-Navas group B.
LINKS
Andrew Elvey Price and A. J. Guttmann, Numerical studies of Thompson's group F and related groups, arXiv:1706.07571 [math.GR], 2017.
EXAMPLE
For n=1 there are 4 words of length 2 equal to the identity: aa^{-1}, a^{-1}a, tt^{-1}, t^{-1}t.
CROSSREFS
Sequence in context: A229651 A229650 A229649 * A229648 A229647 A229646
KEYWORD
nonn,walk
AUTHOR
Andrew Elvey Price, Jan 11 2023
STATUS
approved