This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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; table; 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. REFERENCES G. Kilibarda and V. Jovovic, "Enumeration of some classes of T_0-hypergraphs", in preparation, 2004. LINKS Eric Weisstein's World of Mathematics, Minimal Cover. FORMULA a(n) = Sum(n!/m!*binomial(2^m-m-1, n-m), m=0..n) = Sum(Stirling1(n, m)*A046165(m), m=0..n). E.g.f.: Sum(x^n*(1+x)^(2^n-n-1)/n!, n=0..infinity). Row sums of A094544. CROSSREFS Cf. A035348, A046165, A094544, A094546. Sequence in context: A129436 A063857 A072654 * A156633 A032073 A032083 Adjacent sequences:  A094542 A094543 A094544 * A094546 A094547 A094548 KEYWORD easy,nonn,tabl,changed AUTHOR Goran Kilibarda, Vladeta Jovovic, May 08 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .