Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Formula For All K-Gonal Numbers that Are Centered   Fix a positive integer k. In this paper, we give a formula in closed form for
all k-polygonal numbers that are also centered k-polygonal.

18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat