A029851 Number of self-converse semigroups of order n.

1, 1, 3, 12, 64, 405, 3312, 44370, 2209839, 623492664

Offset: 0

Author

Christian G. Bower, Jan 27 1998, updated Feb 19 2001

Keywords

• nonn
• hard
• more
• nice

Links

• 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

Crossrefs

Cf. A001423, A001426, A027851.

Formula

a(n) = A001423(n)*2 - A027851(n).

Extensions

a(8) and a(9) from Andreas Distler, Jan 17 2011