

A094546


Number of nmember minimal T_0covers.


3




OFFSET

0,3


COMMENTS

A cover of a set is a T_0cover 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_0hypergraphs", in preparation, 2004.


LINKS

G. C. Greubel, Table of n, a(n) for n = 0..8
Eric Weisstein's World of Mathematics, Minimal Cover.


FORMULA

a(n) = Sum_{m=n..2^n1} m!/n!*binomial(2^nn1, mn).


MATHEMATICA

Table[Sum[(m!/n!)*Binomial[2^n  n  1, m  n], {m, n, 2^n  1}], {n, 0, 5}] (* G. C. Greubel, Oct 07 2017 *)


PROG

(PARI) for(n=0, 5, print1(sum(m=n, 2^n 1, (m!/n!)*binomial(2^nn1, mn)), ", ")) \\ G. C. Greubel, Oct 07 2017


CROSSREFS

Cf. A035348, A046165, A094545.
Column sums of A094544.
Sequence in context: A030271 A301576 A160088 * A203035 A030253 A278549
Adjacent sequences: A094543 A094544 A094545 * A094547 A094548 A094549


KEYWORD

easy,nonn,tabl


AUTHOR

Goran Kilibarda, Vladeta Jovovic, May 08 2004


STATUS

approved



