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A264899 Number of nonisomorphic n-element left regular bands. 0
1, 2, 6, 23, 109, 630, 4329, 34458 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Computed by Evan Chen for n<7 using Sage 6.9 and Yongyi Chen for n<9 using Python.

LINKS

Table of n, a(n) for n=1..8.

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

Adjacent sequences:  A264896 A264897 A264898 * A264900 A264901 A264902

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

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Last modified May 8 12:46 EDT 2021. Contains 343666 sequences. (Running on oeis4.)