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A005431
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Embeddings of n-bouquet in sphere.
(Formerly M3674)
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2
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1, 1, 4, 40, 672, 16128, 506880, 19768320, 922521600, 50185175040, 3120605429760, 218442380083200, 17004899126476800, 1457562782269440000, 136427876420419584000, 13847429456672587776000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| K. Casteels and B. Stevens, Universal cycles of (n-1)-partitions of an n-set, Discr. Math., 309 (2009), 5332-5340. See Cor. 12 [From N. J. A. Sloane, Sep 15 2009]
J. L. Gross et al., Genus distributions for bouquets of circles, J. Combin. Theory, B 47 (1989), 292-306.
J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 649.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..200
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FORMULA
| a(n) = 4(2n-3)(n-2)*a(n-1)/n, for n > 2, the sequence shifted by 1.
a(n) = 2^n * (2n-1)!/(n+1)!, for n > 0.
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MATHEMATICA
| Join[{1}, Table[2^n(2n-1)!/(n+1)!, {n, 20}]] (* From Harvey P. Dale, Oct 25 2011 *)
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PROG
| (MAGMA) [1], [2^n * Factorial(2*n-1)/Factorial(n+1): n in [1..20]]; // Vincenzo Librandi, Oct 26 2011
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CROSSREFS
| Sequence in context: A049308 A205671 A181088 * A153849 A010792 A064422
Adjacent sequences: A005428 A005429 A005430 * A005432 A005433 A005434
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KEYWORD
| easy,nonn,nice
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AUTHOR
| Simon Plouffe, N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Description corrected Apr 15 1998 by Wim van Dam (wimvdam(AT)mildred.physics.ox.ac.uk)
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