Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A recursion for divisor function over divisors belonging to a prescribed
  finite sequence of positive integers and a solution of the Lahiri problem for
  divisor function $\sigma_x(n)$   For a finite sequence of positive integers $A=\{a_j\}_{j=1}^{k},$ we prove a
recursion for divisor function $\sigma_{x}^{(A)}(n)=\sum_{d|n,\enskip d\in
A}d^x.$ As a corollary, we give an affirmative solution of the problem posed in
1969 by D. B. Lahiri [3]: to find an identity for divisor function
$\sigma_x(n)$ similar to the classic pentagonal recursion in case of $x=1.$

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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: stat