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A001851 Total diameter of unlabeled trees with n nodes.
(Formerly M1363 N0527)
0
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)
OFFSET
1,3
COMMENTS
C program around function Gen() by Gang Li & Frank Ruskey. See C program link.
REFERENCES
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).
LINKS
W. Bomfim, C program
J. Riordan, Enumeration of trees by height and diameter, IBM J. Res. Dev. 4 (1960), 473-478.
J. Riordan, The enumeration of trees by height and diameter, IBM Journal 4 (1960), 473-478. (Annotated scanned copy)
EXAMPLE
See the trees in first Bomfim link. So a(6) = 21.
CROSSREFS
Sequence in context: A097163 A117186 A155042 * A356375 A303963 A304349
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jul 26 2010
a(21)-a(30) from Washington Bomfim, Jan 31 2011
STATUS
approved

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Last modified May 28 11:56 EDT 2024. Contains 372913 sequences. (Running on oeis4.)