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A137568
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Number of chromatically unique simple graphs on n nodes.
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2
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..9.
Eric Weisstein's World of Mathematics, Chromatically Unique Graph
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FORMULA
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A137568(n) = A000088(n) - A137567(n).
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PROG
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(Sage)
def A137568(n):
....d = {}
....for g in graphs(n):
........c = g.chromatic_polynomial()
........d[c] = 1 if c not in d else d[c]+1
....return d.values().count(1) # [D. S. McNeil, Jan 02 2011]
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CROSSREFS
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Cf. A137567.
Sequence in context: A217929 A151378 A192464 * A010355 A171880 A171874
Adjacent sequences: A137565 A137566 A137567 * A137569 A137570 A137571
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KEYWORD
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nonn,more,hard
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AUTHOR
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Eric W. Weisstein, Jan 26, 2008
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EXTENSIONS
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a(9) from Eric W. Weisstein, Apr 07 2008
a(8) and a(9) corrected by Eric W. Weisstein, Jan 02 2011
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STATUS
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approved
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