Journal of Integer Sequences, Vol. 13 (2010), Article 10.3.5

Finite Topologies and Partitions


Moussa Benoumhani and Messaoud Kolli
Faculty of Science
Department of Mathematics
King Khaled University
Abha
Saudi Arabia

Abstract:

Let E be a set with n elements, and let T(n,k) be the number of all labeled topologies having k open sets that can be defined on E. In this paper, we compute these numbers for k ≤ 17, and arbitrary n, as well as tN0(n,k), the number of all unlabeled non-T0 topologies on E with k open sets, for 3 ≤ k ≤ 8.


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(Concerned with sequences A000798 A001930 A008277 A122934.)

Received September 11 2007; revised versions received October 18 2007; July 7 2009; January 19 2010; March 6 2010. Published in Journal of Integer Sequences, March 10 2010. Minor revision, March 18 2010.


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