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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
OFFSET
2,1
LINKS
R. Kreminski, Graphs and matrices in the study of (finite) topological spaces, Missouri J. Mathematical Sciences, Volume 12 (Issue #2, Spring 2000).
CROSSREFS
Sequence in context: A306681 A254334 A375093 * A299597 A143014 A202907
KEYWORD
nonn,nice,more
AUTHOR
Richard M Kreminski (kremin(AT)boisdarc.tamu-commerce.edu)
STATUS
approved