|
|
A118099
|
|
Number of inverse semigroups of order <= n.
|
|
0
|
|
|
1, 3, 8, 24, 76, 284, 1195, 5832, 32254, 201417, 1400068, 10724115, 89584802, 809190807, 7844705449
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
REFERENCES
|
M. V. Lawson, Inverse Semigroups: The Theory of Partial Symmetries. Singapore: World Scientific, 1999.
E. S. Lyapin, Semigroups. Providence, RI: Amer. Math. Soc., 1974.
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
a(7) = 1195 = 1 + 2 + 5 + 16 + 52 + 208 + 911.
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|