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A122082
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Number of unlabeled bicolored graphs on 2n nodes which are invariant when the two color classes are interchanged.
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2
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1, 2, 5, 16, 67, 404, 3904, 64840, 1930842, 104698904, 10401039400, 1900637187280, 641429385018832, 401454435464761376, 467919402404052870944, 1019758699013228238271040, 4171161230867751509749228304
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1976.
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FORMULA
| a(n) = 2*A007139(n)-A002724(n). - Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 27 2007
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CROSSREFS
| Sequence in context: A019504 A005163 A006116 * A002631 A107948 A058673
Adjacent sequences: A122079 A122080 A122081 * A122083 A122084 A122085
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Oct 18 2006
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Feb 27 2007
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