Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: An identity involving number of representations of $n$ as a sum of $r$
  triangular numbers
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th