Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pattern avoidance in "flattened" partitions   To flatten a set partition (with apologies to Mathematica) means to form a
permutation by erasing the dividers between its blocks. Of course, the result
depends on how the blocks are listed. For the usual listing--increasing entries
in each block and blocks arranged in increasing order of their first
entries--we count the partitions of [n] whose flattening avoids a single
3-letter pattern. Five counting sequences arise: a null sequence, the powers of
2, the Fibonacci numbers, the Catalan numbers, and the binomial transform of
the Catalan numbers.

31
The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
19
The categories of this paper are: eess
1
The categories of this paper are: cs
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas