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A137813
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Minimal number of points needed to make a topology having k open sets.
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1
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0, 1, 2, 2, 3, 3, 4, 3, 4, 4, 5, 4, 5, 5, 5, 4, 5, 5, 6, 5, 6, 6, 6, 5, 6, 6, 6, 6, 7, 6, 7, 5, 6, 6, 7, 6, 7, 7, 7, 6, 7, 7, 7, 7, 7, 7, 8, 6, 7, 7, 7, 7, 8, 7, 8, 7, 8, 8, 8, 7, 8, 8, 8, 6, 7, 7, 8, 7, 8, 8, 8, 7, 8, 8, 8, 8, 8, 8, 9, 7, 8, 8, 8, 8, 8, 8, 9, 8, 9, 8, 9, 8, 9, 9, 9, 7, 8, 8, 8, 8, 9, 8, 9, 8, 9
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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REFERENCES
| K. Ragnarsson and B. E. Tenner, Obtainable sizes of topologies on finite sets, J. Combin. Theory Ser. A 117 (2010) 138-151.
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EXAMPLE
| A topology having 7 open sets can be made on 4 points. The open sets are: {}, {1}, {2}, {1,2}, {1,3}, {1,2,3}, {1,2,3,4}. No topology having 7 open sets can be made with fewer points.
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CROSSREFS
| Cf. A137814.
Sequence in context: A139141 A122953 A128998 * A003313 A117497 A117498
Adjacent sequences: A137810 A137811 A137812 * A137814 A137815 A137816
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KEYWORD
| nonn
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AUTHOR
| Bridget Eileen Tenner (bridget(AT)math.depaul.edu), Feb 11 2008
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