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A029851
Number of self-converse semigroups of order n.
7
1, 1, 3, 12, 64, 405, 3312, 44370, 2209839, 623492664
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OFFSET
0,3
LINKS
Table of n, a(n) for n=0..9.
Andreas Distler,
Classification and Enumeration of Finite Semigroups
, A Thesis Submitted for the Degree of PhD, University of St Andrews (2010).
Eric Weisstein's World of Mathematics,
SemiGroup.
Index entries for sequences related to semigroups
FORMULA
a(n) =
A001423
(n)*2 -
A027851
(n).
CROSSREFS
Cf.
A001423
,
A001426
,
A027851
.
Sequence in context:
A326557
A308204
A307724
*
A201720
A207557
A235129
Adjacent sequences:
A029848
A029849
A029850
*
A029852
A029853
A029854
KEYWORD
nonn
,
hard
,
more
,
nice
AUTHOR
Christian G. Bower
, Jan 27 1998, updated Feb 19 2001
EXTENSIONS
a(8) and a(9) from
Andreas Distler
, Jan 17 2011
STATUS
approved
