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A007142
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E-trees with at most 3 colors.
(Formerly M2989)
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1
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1, 3, 15, 73, 387, 2106, 11998, 69999, 418104, 2540368, 15660843, 97692822, 615559931, 3911866377, 25044058215, 161369414590, 1045681767924, 6810222330303, 44552627690401, 292642818035352, 1929238465836366, 12760620159195044
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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REFERENCES
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G. Gati, F. Harary and R. W. Robinson, Line colored trees with extendable automorphisms, Acta Math. Scientia, 2 (1982), 105-110.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Table of n, a(n) for n=1..22.
G. Gati, F. Harary, R. W. Robinson, Line colored trees with extendable automorphisms, Acta Mathematica Scientia 2.1 (1982), 105-110. (Annotated scanned copy)
Index entries for sequences related to trees
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FORMULA
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a(n) = E(3, n) where E(c, n) is defined in A007141. - Sean A. Irvine, Oct 29 2017
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CROSSREFS
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Sequence in context: A232289 A055837 A124543 * A224397 A190010 A151326
Adjacent sequences: A007139 A007140 A007141 * A007143 A007144 A007145
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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More terms from Sean A. Irvine, Oct 29 2017
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STATUS
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approved
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