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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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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; refs; listen; history; internal format)
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OFFSET
| 0,1
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REFERENCES
| 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.
J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 368 and 631.
G. Ringel and J. W. T. Youngs, Solution of the Heawood map-coloring problem, Proc. Nat. Acad. Sci. USA, 60 (1968), 438-445.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| 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
| a(n) = floor((7+sqrt(1+24*n))/2).
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MATHEMATICA
| Floor[(7+Sqrt[1+24*Range[0, 80]])/2] (* From Harvey P. Dale, Feb 03 2012 *)
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CROSSREFS
| Cf. A000934 (the orientable case).
Sequence in context: A201564 A200303 A198882 * A011275 A205684 A006185
Adjacent sequences: A000700 A000701 A000702 * A000704 A000705 A000706
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KEYWORD
| nonn,nice,changed
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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