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Number of length n permutations that are sorted to the identity by a consecutive-213-avoiding stack followed by a classical-21-avoiding stack.
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%I #15 Sep 25 2020 11:52:44

%S 1,2,5,15,50,180,686,2731

%N Number of length n permutations that are sorted to the identity by a consecutive-213-avoiding stack followed by a classical-21-avoiding stack.

%H C. Defant and K. Zheng, <a href="https://arxiv.org/abs/2008.12297">Stack-Sorting with Consecutive-Pattern-Avoiding Stacks</a>, arXiv:2008.12297 [math.CO], 2020.

%e For n = 3, the permutations 123, 213, 231, 312, and 321 are correctly sorted to the identity while the permutation 132 is not.

%Y Cf. A000108, A001006, A002026, A011782, A202062, A294790.

%K nonn,more

%O 1,2

%A _Kai Zheng_, Aug 30 2020