A151823 Number of nonequivalent monoids of order n with more than one invertible element.

0, 1, 2, 9, 30, 213, 1757, 22956, 955569, 1853259264

Offset: 1

Author

N. J. A. Sloane, Jul 10 2009

Keywords

• nonn

Comments

a(n) is also the number of nonequivalent monoids with nontrivial unit group. [From Tom Kelsey (tom(AT)cs.st-and.ac.uk), Apr 01 2010]

Links

• Andreas Distler and Tom Kelsey, The Monoids of Order Eight and Nine, in: Intelligent Computer Mathematics, Lecture Notes in Computer Science, Volume 5144/2008, pp. 61-76, Springer-Verlag.
• Andreas Distler and Tom Kelsey, The Monoids of Orders Eight, Nine & Ten, Annals of Mathematics and Artificial Intelligence, 56 (2009), 3-25. [From Tom Kelsey (tom(AT)cs.st-and.ac.uk), Apr 01 2010]

Crossrefs

Cf. A001423, A058133.

Extensions

Definition corrected by Tom Kelsey (tom(AT)cs.st-andrews.ac.uk), Apr 01 2010

Corrected and extended by Tom Kelsey (tom(AT)cs.st-and.ac.uk), Apr 01 2010