Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: A sign-reversing involution to count labeled lone-child-avoiding trees
28
The categories of this paper are: alg-geom
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con