A New Quantity Counted by OEIS Sequence A006012

2017/06/21 by Biers-Ariel, Yonah
#05A05 #Combinatorics (math.CO) #FOS: Mathematics

paper · doi:10.48550/arxiv.1706.07064

Abstract

We prove an existing conjecture that the sequence defined recursively by a₁=1, a₂=2, a_n=4a_n-1-2a_n-2 counts the number of length-n permutations avoiding the four generalized permutation patterns 1-32-4, 1-42-3, 2-31-4, and 2-41-3.

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