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A097173
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Total number of green nodes among tricolored labeled trees on n nodes.
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4
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0, 2, 0, 48, 120, 4560, 35700, 1048992, 15514128, 456726240, 10073339100, 323266492560, 9361060088952, 336767513038320, 11913610172869860, 482920107426039360, 19998225191360977440, 909512248720724321472
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| S. Coulomb and M. Bauer, On vertex covers, matchings and random trees
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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)].
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CROSSREFS
| Cf. A097170, A097171, A097172, A097174, A000272.
Sequence in context: A012445 A012450 A158194 * A009493 A009718 A198799
Adjacent sequences: A097170 A097171 A097172 * A097174 A097175 A097176
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KEYWORD
| nonn
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AUTHOR
| Ralf Stephan, Jul 30 2004
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