

A334252


Number of closure operators on a set of n elements which satisfy the T_0 separation axiom.


2




OFFSET

0,2


COMMENTS

The T_0 axiom states that the closure of {x} and {y} are different for distinct x and y.


LINKS



FORMULA



EXAMPLE

The a(0) = 1 through a(2) = 5 setsystems of closed sets:
{{}} {{}} {{1,2},{1}}
{{1},{}} {{1,2},{2}}
{{1,2},{1},{}}
{{1,2},{2},{}}
{{1,2},{1},{2},{}}


CROSSREFS

The number of all closure operators is given in A102896.
For strict T0 closure operators, see A334253.
For T1 closure operators, see A334254.


KEYWORD

nonn,more


AUTHOR



EXTENSIONS



STATUS

approved



