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 A097174 Total number of red nodes among tricolored labeled trees on n nodes. 6
 1, 0, 6, 12, 320, 2190, 51492, 685496, 17286768, 348213690, 9956411300, 266065478052, 8737396913544, 287741445880070, 10816320294520860, 420123621828718320, 17913098835916877792, 798053882730994171890 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS G. C. Greubel, Table of n, a(n) for n = 1..385 S. Coulomb and M. Bauer, On vertex covers, matchings and random trees FORMULA E.g.f.: A(x) = -T(-T(x)), with T(x) = Sum_{k>=1} A000169(k)/k!*x^k. a(n) = -n^(n-1) * Sum[l=1..n, (-l/n)^l*C(n, l)]. a(n) ~ LambertW(1)*n^(n-1)/(1+LambertW(1)). - Vaclav Kotesovec, Aug 26 2016 MATHEMATICA Rest[CoefficientList[Series[LambertW[-LambertW[-x]], {x, 0, 20}], x] * Range[0, 20]!] (* Vaclav Kotesovec, Aug 26 2016 *) PROG (PARI) x='x+O('x^50); Vec(serlaplace(lambertw(-lambertw(-x)))) \\ G. C. Greubel, Nov 15 2017 CROSSREFS Cf. A097170, A097171, A097172, A097173, A000272. Sequence in context: A181493 A051784 A158046 * A191415 A259130 A032511 Adjacent sequences:  A097171 A097172 A097173 * A097175 A097176 A097177 KEYWORD nonn AUTHOR Ralf Stephan, Jul 30 2004 STATUS approved

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Last modified February 18 05:36 EST 2019. Contains 320245 sequences. (Running on oeis4.)