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Search: id:A006057
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| A006057 |
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Number of labeled topologies with n points.
(Formerly M3028)
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+0
5
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| 1, 1, 3, 16, 137, 1826, 37777, 1214256, 60075185, 4484316358, 493489876721, 78456654767756, 17735173202222665, 5630684018989523274, 2486496790249207981169, 1515191575312017416011456
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
M. Erne', Struktur- und Anzahlformeln fuer Topologien auf Endlichen Mengen, Manuscripta Math., 11 (1974), 221-259.
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LINKS
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Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 02 2008, Table of n, a(n) for n = 0..19
P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.
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FORMULA
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E.g.f.: A04(x)=exp(Z04(x)-1) where Z04(x) denotes the E.g.f. for A006059. - Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 02 2008
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CROSSREFS
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Cf. A000798.
Sequence in context: A119392 A129043 A135746 this_sequence A002719 A020554 A062874
Adjacent sequences: A006054 A006055 A006056 this_sequence A006058 A006059 A006060
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 02 2008
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