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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

Table of n, a(n) for n=1..30.

W. Bomfim, Diameters of the trees of order 6

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)

Index entries for sequences related to trees

EXAMPLE

See the trees in first Bomfim link. So a(6) = 21.

CROSSREFS

Sequence in context: A097163 A117186 A155042 * A303963 A304349 A024822

Adjacent sequences:  A001848 A001849 A001850 * A001852 A001853 A001854

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

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 October 17 05:23 EDT 2018. Contains 316275 sequences. (Running on oeis4.)