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A028855 Number of prime unlabeled topologies (i.e., prime homeomorphism classes) on n points. 0
3, 9, 27, 139, 691, 4535 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

REFERENCES

R. Kreminski, "Graphs and matrices in the study of (finite) topological spaces", Missouri J. Mathematical Sciences, Volume 12 (Issue #2, Spring 2000).

LINKS

Table of n, a(n) for n=2..7.

Missouri J. Mathematical Sciences (New web address)

CROSSREFS

Sequence in context: A146151 A306681 A254334 * A299597 A143014 A202907

Adjacent sequences:  A028852 A028853 A028854 * A028856 A028857 A028858

KEYWORD

nonn,nice

AUTHOR

Richard M Kreminski (kremin(AT)boisdarc.tamu-commerce.edu)

STATUS

approved

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Last modified October 24 12:04 EDT 2021. Contains 348225 sequences. (Running on oeis4.)