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Search: id:A001928
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| A001928 |
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Number of connected topologies with n unlabeled nodes.
(Formerly M1655 N0648)
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+0
4
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| 1, 1, 2, 6, 21, 94, 512, 3485, 29515, 314474, 4255727, 73831813, 1653083021, 47941962135, 1803010446411, 87882300251730, 5543501326580737
(list; graph; listen)
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OFFSET
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0,3
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REFERENCES
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K. K.-H. Butler and G. Markowsky, Enumeration of finite topologies, Proc. 4th S-E Conf. Combin., Graph Theory, Computing, Congress. Numer. 8 (1973), 169-184.
J. A. Wright, There are 718 6-point topologies, quasi-orderings, and transgraphs, Notices Amer. Math. Soc., 17 (1970), p. 646, Abstract #70T-A106.
J. A. Wright, personal communication.
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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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Inverse Euler transform of A001930. - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 06 2006
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CROSSREFS
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Cf. A001929, A001930.
Sequence in context: A090805 A033540 A115089 this_sequence A005638 A008988 A061232
Adjacent sequences: A001925 A001926 A001927 this_sequence A001929 A001930 A001931
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KEYWORD
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nonn
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AUTHOR
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njas
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EXTENSIONS
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More terms from Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 06 2006
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