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A029851
Number of self-converse semigroups of order n.
7
1, 1, 3, 12, 64, 405, 3312, 44370, 2209839, 623492664
(list; graph; refs; listen; history; text; internal format)
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. A001426.
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

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Last modified October 21 01:21 EDT 2024. Contains 376963 sequences.
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