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Search: id:A000664
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| A000664 |
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Number of graphs with n edges.
(Formerly M1400 N0545)
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+0
5
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| 1, 1, 2, 5, 11, 26, 68, 177, 497, 1476, 4613, 15216, 52944, 193367, 740226, 2960520, 12334829, 53394755, 239544624, 1111261697, 5320103252, 26237509076, 133087001869, 693339241737, 3705135967663, 20286965943329, 113694201046379
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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These are simple graphs, unlabeled, with no isolated nodes, but are not necessarily connected.
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REFERENCES
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W. Oberschelp, Kombinatorische Anzahlbestimmungen in Relationen, Math. Ann., 174 (1967), 53-78.
J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 146.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
M. L. Stein and P. R. Stein, Enumeration of Linear Graphs and Connected Linear Graphs up to $p = 18$ Points. Report LA-3775, Los Alamos Scientific Laboratory of the University of California, Los Alamos, NM, Oct 1967.
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LINKS
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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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Euler transform of A002905 (ignoring A002905(0)). - Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net) Jul 03 2009
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EXAMPLE
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n=1: o-o (1)
n=2: o-o o-o, o-o-o (2)
n=3: o-o o-o o-o, o-o-o o-o, o-o-o-o, Y, triangle (5)
n=4: o-o o-o o-o o-o, o-o-o o-o o-o, o-o-o o-o-o, o-o o-o-o-o, o-o Y, o-o triangle,
o-o-o-o-o, >o-o-o, ><, square, triangle with tail (11)
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CROSSREFS
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Cf. A008406.
Sequence in context: A025245 A079223 A095892 this_sequence A067922 A095975 A006652
Adjacent sequences: A000661 A000662 A000663 this_sequence A000665 A000666 A000667
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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 Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 08 2000, Aug 14 2007
Edited by N. J. A. Sloane (njas(AT)research.att.com), Feb 26 2008
Example for n=2 corrected by Adrian Falcone (falcone(AT)gmail.com), Jan 28 2009
Zero term inserted by Franklin T. Adams-Watters (FrankTAW(AT)Netscape.net), Jul 03 2009
a(25)-a(26) from Max Alekseyev (maxale(AT)gmail.com), Sep 19 2009
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