Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A recursive algorithm for trees and forests   Trees or rooted trees have been generously studied in the literature. A
forest is a set of trees or rooted trees. Here we give recurrence relations
between the number of some kind of rooted forest with $k$ roots and that with
$k+1$ roots on $\{1,2,\ldots,n\}$. Classical formulas for counting various
trees such as rooted trees, bipartite trees, tripartite trees, plane trees,
$k$-ary plane trees, $k$-edge colored trees follow immediately from our
recursive relations.

8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
17
The categories of this paper are: q-fin
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas