OFFSET
0,4
COMMENTS
A cover of a set is a T_0-cover if for every two distinct points of the set there exists a member (block) of the cover containing one but not the other point.
Row sums of A094544.
LINKS
Goran Kilibarda and Vladeta Jovovic, Enumeration of some classes of T_0-hypergraphs, arXiv:1411.4187 [math.CO], 2014.
Eric Weisstein's World of Mathematics, Minimal Cover.
FORMULA
a(n) = Sum_{m=0..n} (n!/m!)*binomial(2^m-m-1, n-m).
a(n) = Sum_{m=0..n} Stirling1(n, m)*A046165(m).
E.g.f.: Sum_{n>=0} x^n*(1+x)^(2^n-n-1)/n!.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Goran Kilibarda and Vladeta Jovovic, May 08 2004
STATUS
approved