Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A noncommutative enumeration problem   In this article we tackle the combinatorics of coloured hard-dimer objects.
This is achieved by identifying coloured hard-dimer configurations with a
certain class of rooted trees that allow for an algebraic treatment in terms of
noncommutative formal power series.

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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
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The categories of this paper are: cs
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: q-bio
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The categories of this paper are: chao-dyn
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The categories of this paper are: gr-qc
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: stat