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A253571 Total number of even outdegree nodes among all labeled rooted trees on n nodes. 1
1, 2, 15, 144, 1765, 26400, 466459, 9508352, 219651849, 5671088640, 161833149511, 5058050224128, 171837337744813, 6304955850432512, 248477268083174355, 10467916801317273600, 469451601966727952401, 22329535184262444220416, 1122809130124800181976575 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Marko Riedel and Alois P. Heinz, Table of n, a(n) for n = 1..380 (first 100 terms from Marko Riedel)

Marko Riedel, Even outdegree nodes among all labeled trees on n nodes

FORMULA

E.g.f: (T^2+z^2)/(2*T*(1-T)) where T is the labeled tree function defined by T = z exp T.

EXAMPLE

When n=3 there are two types of trees: rooted paths on three nodes which have one even degree node (the bottom one with zero children), giving 6x1 and trees consisting of a node with two children, of which there are 3, and they have 3 even degree nodes, giving 3x3 for a total of 6x1+3x3 = 15.

MAPLE

a:= n-> n!*coeff(series((T->(T^2+x^2)/

    (2*T*(1-T)))(-LambertW(-x)), x, n+2), x, n):

seq(a(n), n=1..30);  # Alois P. Heinz, Jan 03 2015

CROSSREFS

Cf. A000169, A026641, A000081.

Sequence in context: A005415 A219868 A224885 * A111686 A001854 A060226

Adjacent sequences:  A253568 A253569 A253570 * A253572 A253573 A253574

KEYWORD

nonn

AUTHOR

Marko Riedel, Jan 03 2015

STATUS

approved

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Last modified February 21 16:28 EST 2018. Contains 299414 sequences. (Running on oeis4.)