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A023814
Number of associative binary operations on an n-set; number of labeled semigroups.
17
1, 1, 8, 113, 3492, 183732, 17061118, 7743056064, 148195347518186, 38447365355811944462
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OFFSET
0,3
LINKS
Table of n, a(n) for n=0..9.
Alex Bailey, Martin Finn-Sell, and Robert Snocken,
Subsemigroup, ideal and congruence growth of free semigroups
, arXiv preprint arXiv:1409.2444 [math.GR], 2014.
A. Distler and T. Kelsey,
The semigroups of order 9 and their automorphism groups
, arXiv preprint arXiv:1301.6023 [math.CO], 2013.
C. Noebauer,
Home page
[broken link]
C. Noebauer,
The Numbers of Small Rings
C. Noebauer,
Thesis on the enumeration of near-rings
Eric Postpischil
Posting to sci.math newsgroup, May 21 1990
Eric Weisstein's World of Mathematics,
Semigroup.
Index entries for sequences related to semigroups
CROSSREFS
Cf.
A001423
,
A001426
,
A023813
,
A023815
,
A027851
.
a(n) +
A079172
(n) =
A002489
(n).
Sequence in context:
A092084
A346985
A099715
*
A217772
A062126
A222520
Adjacent sequences:
A023811
A023812
A023813
*
A023815
A023816
A023817
KEYWORD
nonn
,
more
AUTHOR
Lyle Ramshaw (ramshaw(AT)pa.dec.com)
EXTENSIONS
a(8), a(9) from Distler and Kelsey (2013). -
N. J. A. Sloane
, Feb 19 2013
STATUS
approved
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Last modified March 28 11:59 EDT 2024. Contains 371254 sequences. (Running on oeis4.)