A058123 Triangle read by rows: semigroups of order n with k idempotents, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).
1, 2, 2, 5, 7, 6, 19, 37, 44, 26, 132, 216, 351, 326, 135, 3107, 1780, 3093, 4157, 2961, 875, 623615, 32652, 33445, 53145, 56020, 30395, 6749, 1834861133, 4665709, 600027, 754315, 1007475, 822176, 348692, 60601, 52976551026562, 12710266442, 68769167, 14050493, 18660074, 20044250, 12889961, 4389418, 618111
Offset: 1
Examples
Triangle starts:
1;
2, 2;
5, 7, 6;
19, 37, 44, 26;
132, 216, 351, 326, 135;
...
Links
- Andrey Zabolotskiy, Table of n, a(n) for n = 1..55 (rows 1-10)
- Andreas Distler, Classification and Enumeration of Finite Semigroups, A Thesis Submitted for the Degree of PhD, University of St Andrews (2010).
- Andreas Distler, Chris Jefferson, Tom Kelsey, Lars Kotthoff, The Semigroups of Order 10, in: M. Milano (Ed.), Principles and Practice of Constraint Programming, 18th International Conference, CP 2012, Québec City, QC, Canada, October 8-12, 2012, Proceedings (LNCS, volume 7514), pp. 883-899, Springer-Verlag Berlin Heidelberg 2012.
- A. Distler and T. Kelsey, The semigroups of order 9 and their automorphism groups, arXiv preprint arXiv:1301.6023 [math.CO], 2013.
- Index entries for sequences related to semigroups
Extensions
More terms from Andreas Distler, Jan 13 2011