Enumerative combinatorics
Journal of Algebraic Combinatorics: An International Journal
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In this paper, we construct explicitly a noncommutative symmetric ( ${\mathcal{N}}$ CS) system over the Grossman-Larson Hopf algebra of labeled rooted trees. By the universal property of the $\mathcal {N}$ CS system formed by the generating functions of certain noncommutative symmetric functions, we obtain a specialization of noncommutative symmetric functions by labeled rooted trees. Taking the graded duals, we also get a graded Hopf algebra homomorphism from the Connes-Kreimer Hopf algebra of labeled rooted forests to the Hopf algebra of quasi-symmetric functions. A connection of the coefficients of the third generating function of the constructed $\mathcal {N}$ CS system with the order polynomials of rooted trees is also given and proved.