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A001851
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Total diameter of unlabeled trees with n nodes.
(Formerly M1363 N0527)
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0
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0, 1, 2, 5, 9, 21, 44, 103, 232, 571, 1368, 3441, 8653, 22263, 57518, 150733, 396937, 1054540, 2815453, 7562159, 20399714, 55280532, 150356806, 410432671, 1123902587, 3086827578, 8500975970, 23470712241, 64952794778, 180144093389
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,3
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COMMENTS
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C program around function Gen() by Gang Li & Frank Ruskey. See C program link.
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REFERENCES
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J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478.
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
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Table of n, a(n) for n=1..30.
Index entries for sequences related to trees
J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478. [From Herman Jamke (hermanjamke(AT)fastmail.fm), Jul 26 2010]
W. Bomfim, Diameters of the trees of order 6
W. Bomfim, C program
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EXAMPLE
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See the trees in first Bomfim link. So a(6) = 21.
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CROSSREFS
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Sequence in context: A097163 A117186 A155042 * A024822 A218966 A029726
Adjacent sequences: A001848 A001849 A001850 * A001852 A001853 A001854
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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 Herman Jamke (hermanjamke(AT)fastmail.fm), Jul 26 2010. a(21)-a(30) from W. Bomfim, jan 31 2011.
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STATUS
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approved
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