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A058737
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Main diagonal of A058735.
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1
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1, 1, 3, 7, 20, 55, 162, 477, 1450, 4446, 13858, 43589, 138515, 443487, 1430261, 4640312, 15137893, 49620637, 163360133, 539904503, 1790699059, 5958280016, 19883532941, 66532519727, 223177199775, 750340752081, 2528058240115
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,3
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COMMENTS
| Also the number of unlabeled cographs on n nodes with two components. - Vladeta Jovovic (vladeta(AT)eunet.rs), May 07 2005
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REFERENCES
| J. Riordan, The blossoming of Schroeder's fourth problem, Acta Math., 137 (1976), 1-16.
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LINKS
| Eric Weisstein's World of Mathematics, Cograph
Index entries for sequences related to rooted trees
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FORMULA
| G.f.: A(x) = (B(x)^2+B(x^2))/2, where B(x) = g.f. for A000669. - Vladeta Jovovic (vladeta(AT)eunet.rs), May 07 2005
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CROSSREFS
| Cf. A106240.
Sequence in context: A109220 A018034 A000227 * A129429 A084204 A030238
Adjacent sequences: A058734 A058735 A058736 * A058738 A058739 A058740
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jan 01 2001
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), May 07 2005
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