Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recursive Procedures for Krall-Sheffer Operators   We consider the Krall-Sheffer class of admissible, partial differential
operators in the plane. We concentrate on algebraic structures, such as the
role of commuting operators and symmetries. For the polynomial eigenfunctions,
we give explicit forms of the the $3-$level recurrence relations and
differential raising operators, which are shown to satisfy unusual commutation
relations. We present new generating functions for two of the cases.

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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: econ
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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: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph