login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A137814 Smallest size (greater than 1) of a topology that cannot be made using n points. 1

%I

%S 3,5,7,11,19,29,47,79,127,191

%N Smallest size (greater than 1) of a topology that cannot be made using n points.

%D K. Ragnarsson and B. E. Tenner, Obtainable sizes of topologies on finite sets, J. Combin. Theory Ser. A 117 (2010) 138-151.

%e There is no topology on 3 points having 7 open sets. However, there do exist topologies on 3 points that have 2, 3, 4, 5 and 6 open sets.

%Y Cf. A137813.

%K nonn

%O 1,1

%A _Bridget Tenner_, Feb 11 2008

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

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

Last modified December 22 21:10 EST 2014. Contains 252372 sequences.