

A007903


The number of distinct principal ideals in the semigroup of binary relations on an nset.


0




OFFSET

1,1


COMMENTS

a(n) is the number of Green's Jclasses in the semigroup of binary relations on an nset.  James Mitchell, May 10 2015


REFERENCES

George Markowsky, 1991; Markowsky and Breen, 1993; Breen, 1995.


LINKS

Table of n, a(n) for n=1..7.
Jin Bai Kim, Tables of dclasses in the semigroup Bn1 of the binary relations on a set x with nelements, Bull. Korean Math. Soc., Volume 20, Issue 1, 1983, pp. 913.
Wikipedia, Green's relations
Index entries for sequences related to semigroups


CROSSREFS

Sequence in context: A091233 A173312 A156434 * A182100 A006894 A193565
Adjacent sequences: A007900 A007901 A007902 * A007904 A007905 A007906


KEYWORD

nonn,hard,more,nice


AUTHOR

Michael A Breen [ MAB1699(AT)tntech.edu ]


STATUS

approved



