A058133 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

A058133

Number of monoids (semigroups with identity) of order n, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).

0, 1, 2, 6, 27, 156, 1373, 17730, 858977, 1844075697, 52991253973742

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

LINKS

Table of n, a(n) for n=0..10.

Eric Postpischil Posting to sci.math newsgroup, May 21 1990

Andreas Distler and Tom Kelsey, The Monoids of Order Eight and Nine. Lecture Notes in Computer Science 5144 (2008), 61-76.

Andreas Distler and Tom Kelsey, The Monoids of Orders Eight, Nine & Ten. Annals of Mathematics and Artificial Intelligence 56 (2009), 3-25.

Index entries for sequences related to monoids

FORMULA

a(n)=(A058129(n)+A058132(n))/2.

CROSSREFS

Cf. A001423, A058129, A058132, A151823.

Sequence in context: A118192 A338180 A307595 * A306857 A321584 A009308

Adjacent sequences: A058130 A058131 A058132 * A058134 A058135 A058136

KEYWORD

nonn,more,hard

AUTHOR

Christian G. Bower, Nov 13 2000

EXTENSIONS

a(8) and a(9) from Distler & Kelsey (2008), added by N. J. A. Sloane, Jul 10 2009

a(10) from Distler & Kelsey (2009), added by Max Alekseyev, Jul 13 2009

a(0) prepended by Jianing Song, Oct 26 2019

STATUS

approved