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A006056 Number of topologies on n labeled points satisfying the T_4 axiom.
(Formerly M3615)
10
1, 1, 4, 26, 255, 3642, 75606, 2316169, 106289210, 7321773414, 748425136289, 111576624613588, 23864968806932886, 7225895692327786931, 3064182503223082011556, 1803904252801640389374494, 1463405916763710662849541695, 1625522872429294851288338156654 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
M. Erné, Struktur- und Anzahlformeln für Topologien auf Endlichen Mengen, Manuscripta Math., 11 (1974), 221-259.
M. Erné, Struktur- und Anzahlformeln für Topologien auf Endlichen Mengen, Manuscripta Math., 11 (1974), 221-259. (Annotated scanned copy)
FORMULA
E.g.f.: A4(X) = exp(Z4(X)-1) where Z4(x) denotes the e.g.f. for A006058. - Herman Jamke, Mar 02 2008
CROSSREFS
Sequences in the Erné (1974) paper: A000798, A001035, A006056, A006057, A001929, A001927, A006058, A006059, A000110.
Sequence in context: A362112 A056786 A350164 * A215242 A098620 A215266
KEYWORD
nonn,nice
AUTHOR
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 02 2008
More precise definition from N. J. A. Sloane, Jan 09 2014
STATUS
approved

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Last modified March 19 07:49 EDT 2024. Contains 370958 sequences. (Running on oeis4.)