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Search: id:A000703
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| A000703 |
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Chromatic number (or Heawood number) of nonorientable surface with n crosscaps.
(Formerly M3265 N1318)
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+0
2
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| 4, 6, 7, 7, 8, 9, 9, 10, 10, 10, 11, 11, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 15, 15, 15, 15, 16, 16, 16, 16, 16, 17, 17, 17, 17, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24
(list; graph; listen)
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OFFSET
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0,1
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
K. Appel and W. Haken, Every planar map is four colorable. I. Discharging. Illinois J. Math. 21 (1977), no. 3, 429-490.
G. A. Dirac, Map-color theorems, Canad. J. Math., 4 (1952), 480ff.
J. L. Gross and T. W. Tucker, Topological Graph Theory, Wiley, 1987; see Table 5.2 p. 221.
G. Ringel and J. W. T. Youngs, Solution of the Heawood map-coloring problem, Proc. Nat. Acad. Sci. USA, 60 (1968), 438-445.
J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 368 and 631.
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LINKS
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T. D. Noe, Table of n, a(n) for n=0..1000
G. Ringel & J. W. T. Youngs, Solution Of The Heawood Map-Coloring Problem
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FORMULA
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a(n) = floor((7+sqrt(1+24*n))/2).
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CROSSREFS
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Cf. A000934 (the orientable case).
Sequence in context: A135798 A021218 A019605 this_sequence A011275 A006185 A021876
Adjacent sequences: A000700 A000701 A000702 this_sequence A000704 A000705 A000706
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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