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 A097173 Total number of green nodes among tricolored labeled trees on n nodes. 4
 0, 2, 0, 48, 120, 4560, 35700, 1048992, 15514128, 456726240, 10073339100, 323266492560, 9361060088952, 336767513038320, 11913610172869860, 482920107426039360, 19998225191360977440, 909512248720724321472 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS S. Coulomb and M. Bauer, On vertex covers, matchings and random trees FORMULA E.g.f.: A(x) = T(-T(x))^2, with T(x)=Sum[k=1..inf, A000169(k)/k!*x^k]. a(n) = -2 * n^(n-1) * Sum[l=1..n, (-l/n)^l*(1/l-1)*C(n, l)]. a(n) ~ 2*LambertW(1)^2*n^(n-1)/(1+LambertW(1)). - Vaclav Kotesovec, Aug 26 2016 MATHEMATICA Rest[CoefficientList[Series[LambertW[-LambertW[-x]]^2, {x, 0, 20}], x] * Range[0, 20]!] (* Vaclav Kotesovec, Aug 26 2016 *) CROSSREFS Cf. A097170, A097171, A097172, A097174, A000272. Sequence in context: A303396 A319113 A158194 * A009493 A009718 A198799 Adjacent sequences:  A097170 A097171 A097172 * A097174 A097175 A097176 KEYWORD nonn AUTHOR Ralf Stephan, Jul 30 2004 STATUS approved

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Last modified February 22 05:17 EST 2019. Contains 320385 sequences. (Running on oeis4.)