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 A094545 Number of minimal T_0-covers of an n-set. 3
 1, 1, 1, 4, 17, 176, 2287, 49540, 1518337, 67457584, 4254836111, 376795261844, 46709151254449, 8061849904932136, 1936383997541071639, 646603398091877815516, 300476951799493029958913 (list; graph; refs; listen; history; text; internal format)
 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 Table of n, a(n) for n=0..16. 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 Cf. A035348, A046165, A094544, A094546. Sequence in context: A063857 A362646 A072654 * A156633 A032073 A032083 Adjacent sequences: A094542 A094543 A094544 * A094546 A094547 A094548 KEYWORD easy,nonn AUTHOR Goran Kilibarda and Vladeta Jovovic, May 08 2004 STATUS approved

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Last modified June 22 05:36 EDT 2024. Contains 373565 sequences. (Running on oeis4.)