A244493 Number of oriented (0, 1, 2)-factors of the Johnson graph J(n, 2).

1, 6, 265, 126140, 855966441, 102526835994056, 258081861682902430193

Offset

2,2

Comments

From James East, Jul 13 2016: (Start)

a(5) and a(6) were calculated by James Mitchell using the GAP System Packages Semigroups (see link).

a(n) is also the number of minimal size all-idempotent generating sets for the singular part of the Brauer monoid (see East-Gray paper). (End)

Links

Table of n, a(n) for n=2..8.

J. East, R. D. Gray, Diagram monoids and Graham-Houghton graphs: idempotents and generating sets of ideals, arXiv:1404.2359 [math.GR], 2014.

GAP, Semigroups

Ronald Niles, C++ project on GitHub

Ronald Niles, Computation of A244493

Prog

(C++) See Niles link.

Crossrefs

Sequence in context: A332126 A229579 A033289 * A221900 A229773 A193983

Adjacent sequences: A244490 A244491 A244492 * A244494 A244495 A244496

Keyword

nonn,more

Author

N. J. A. Sloane, Jul 05 2014

Extensions

Name clarified by James East, Jul 14 2016

a(6) corrected and a(7) added by Ronald Niles, Apr 21 2017

a(8) added by Ronald Niles, Jun 25 2017

Status

approved