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A093377
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Number of labeled n-vertex graphs without 2-components and without isolated vertices(1-components).
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1
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1, 0, 0, 4, 38, 728, 26864, 1871576, 251762204, 66308767200, 34497665550400, 35641856042561008, 73354660691960203016, 301272244237002052739424, 2471648864359822034978330304, 40527681073171940835893232576032
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Also number of unlabeled n-block ordered r-bicoverings, cf. A060053. - Vladeta Jovovic (vladeta(AT)eunet.rs), May 13 2004
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..65
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FORMULA
| E.g.f. exp(-x-x^2/2)*Sum(2^binomial(n, 2)*x^n/n!, n=0..infinity). Inverse binomial transform of A093352().
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PROG
| (PARI) N=66; x='x+O('x^N); /* that many terms */
egf=exp(-x-x^2/2)*sum(i=0, N, 2^binomial(i, 2)*x^i/i!);
Vec(serlaplace(egf)) /* show terms */
/* Joerg Arndt, Jul 06 2011 */
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CROSSREFS
| Cf. A006129, A093351, A093352.
Sequence in context: A084285 A084286 A001187 * A178017 A131591 A030259
Adjacent sequences: A093374 A093375 A093376 * A093378 A093379 A093380
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KEYWORD
| nonn
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AUTHOR
| Goran Kilibarda, Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 28 2004
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