Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Four Variations on Graded Posets   We explore the enumeration of some natural classes of graded posets,
including all graded posets, (2+2)- and (3+1)-avoiding graded posets,
(2+2)-avoiding graded posets, and (3+1)-avoiding graded posets. We obtain
enumerative and structural theorems for all of them. Along the way, we discuss
a situation when we can switch between enumeration of labeled and unlabeled
objects with ease, generalize a result of Postnikov and Stanley from the theory
of hyperplane arrangements, answer a question posed by Stanley, and see an old
result of Klarner in a new light.

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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
8
The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg