Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a conjecture regarding primality of numbers constructed from
  prepending and appending identical digits   Consider the operation of adding the same number of identical digits to the
left and to the right of a number n. In OEIS sequence A090287, it was
conjectured that this operation will not produce a prime if and only if n is a
palindrome with an even number of digits. We show that this conjecture is false
by showing that this property also holds for n=231, n=420, and an infinite
number of other values of n.

30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th