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A006056
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Number of topologies on n labeled points satisfying the T_4 axiom.
(Formerly M3615)
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10
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1, 1, 4, 26, 255, 3642, 75606, 2316169, 106289210, 7321773414, 748425136289, 111576624613588, 23864968806932886, 7225895692327786931, 3064182503223082011556, 1803904252801640389374494, 1463405916763710662849541695, 1625522872429294851288338156654
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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).
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LINKS
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FORMULA
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E.g.f.: A4(X) = exp(Z4(X)-1) where Z4(x) denotes the e.g.f. for A006058. - Herman Jamke, Mar 02 2008
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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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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STATUS
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approved
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