

A007903


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


1




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

K. H. Kim, Boolean Matrix Theory and Applications, Marcel Decker Inc., 1982.
George Markowsky, 1991; Markowsky and Breen, 1993; Breen, 1995.


LINKS



FORMULA

a(n) is asymptotic to 2^(n^2)/n!^2 (from Kim reference).  Geoffrey Critzer, May 14 2023


CROSSREFS



KEYWORD

nonn,hard,more,nice


AUTHOR

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


STATUS

approved



