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A276409
Number of reduced words of length n in the alphabet {U,U^(-1),S,S^(-1)} that are equal to unity if U^3 = S^2 = 1.
2
1, 0, 2, 2, 6, 24, 44, 136, 298, 914, 2462, 6464, 17740, 47840, 133618, 366162, 1011190, 2801144, 7775916, 21680712, 60443514, 168963010, 472975278, 1326349568, 3725180524, 10475012672, 29494512354, 83141905570, 234634612198, 662840458840, 1874315939756
OFFSET
0,3
LINKS
G. Alkauskas, The modular group and words in its two generators, arXiv:1512.02596 [math.NT], 2015-2017.
G. Alkauskas, The modular group and words in its two generators, Lithuanian Math. J. 57(1) (2017), 1-12.
Jason Bell and Marni Mishna, On the Complexity of the Cogrowth Sequence, arXiv:1805.08118 [math.CO], 2018.
CROSSREFS
Sequence in context: A188962 A076741 A320603 * A093453 A301381 A342282
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 14 2016
EXTENSIONS
Name changed, terms a(12) and beyond added using g.f. from Alkauskas by Andrey Zabolotskiy, Aug 03 2022
STATUS
approved