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A027851
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Number of nonisomorphic semigroups of order n.
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16
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OFFSET
| 0,3
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REFERENCES
| A. de Vries, Formal Languages: An Introduction, http://haegar.fh-swf.de/Seminare/Genome/Archiv/languages.pdf
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LINKS
| Andreas Distler, Classification and Enumeration of Finite Semigroups, A Thesis Submitted for the Degree of PhD, University of St Andrews (2010).
Eric Postpischil Posting to sci.math newsgroup, May 21 1990
C. Noebauer, Home page
C. Noebauer, The Numbers of Small Rings
C. Noebauer, Thesis on the enumeration of near-rings
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Index entries for sequences related to semigroups
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CROSSREFS
| a(n)=A001423(n)*2-A029851(n). Cf. A001426, A023814, A058108.
a(n)+A079173(n)=A001329(n)
Sequence in context: A009601 A009676 A192995 * A120765 A051812 A003224
Adjacent sequences: A027848 A027849 A027850 * A027852 A027853 A027854
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KEYWORD
| nonn,hard,nice
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AUTHOR
| Christian G. Bower (bowerc(AT)usa.net), Dec 13 1997, updated Feb 19 2001
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EXTENSIONS
| a(8)-a(9) from Andreas Distler (andreas(AT)mcs.st-andrews.ac.uk), Jan 13 2011
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