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A264899
Number of nonisomorphic n-element left regular bands.
0
1, 2, 6, 23, 109, 630, 4329, 34458
OFFSET
1,2
COMMENTS
Computed by Evan Chen for n<7 using Sage 6.9 and Yongyi Chen for n<9 using Python.
LINKS
K. S. Brown, Semigroups, rings, and Markov chains, arXiv:math/0006145 [math.PR], 2000.
K. S. Brown, Semigroups, rings, and Markov chains, J. Theoretical Prob. 13 (2000), 871-938.
EXAMPLE
For n=2 the two LRBs have elements x,y and relations (1) x^2=xy=yx=x, y^2=y, (2) y^2=xy=y, x^2=yx=x.
CROSSREFS
Sequence in context: A328441 A328507 A208733 * A224786 A320566 A205802
KEYWORD
nonn,more
AUTHOR
Richard Stanley, Nov 27 2015
EXTENSIONS
a(7)-a(8) from Yongyi Chen entered by Richard Stanley, Nov 30 2015
STATUS
approved