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A006343
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Arkons: number of elementary maps with n-1 nodes.
(Formerly M3400)
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1
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1, 0, 1, 1, 4, 10, 34, 112, 398, 1443, 5387, 20482, 79177, 310102, 1228187, 4910413, 19792582, 80343445, 328159601, 1347699906, 5561774999, 23052871229, 95926831442, 400587408251, 1678251696379, 7051768702245, 29710764875014
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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REFERENCES
| K. Appel and W. Haken, Every planar map is four colorable. With the collaboration of J. Koch. Contemporary Mathematics, 98. American Mathematical Society, Providence, RI, 1989. xvi+741 pp. ISBN: 0-8218-5103-9.
F. R. Bernhart, Topics in Graph Theory Related to the Five Color Conjecture. Ph.D. Dissertation, Kansas State Univ., 1974.
F. R. Bernhart, Catalan, Motzkin and Riordan numbers, Discr. Math., 204 (1999) 73-112.
G. D. Birkhoff and D. C. Lewis, Chromatic polynomials. Trans. Amer. Math. Soc. 60, (1946). 355-451.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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FORMULA
| a(n-1) = Sum (n-k-1)^(-1)*binomial(n, k)*binomial(2*n-3*k-4, n-2*k-2); k = 0..[ (n-2)/2 ], n >= 3.
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CROSSREFS
| Cf. A000934.
Sequence in context: A100507 A156700 A182645 * A149173 A149174 A030003
Adjacent sequences: A006340 A006341 A006342 * A006344 A006345 A006346
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KEYWORD
| easy,nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Erroneously duplicated term 4 removed per Frank Bernhart's report Max Alekseyev (maxale(AT)gmail.com), Feb 11 2010
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