A337522 Number of permutations of length n that are sorted to the identity by a consecutive-312-avoiding-stack followed by a classical-21-avoiding stack.

1, 1, 2, 5, 15, 50, 179, 675, 2649, 10734

Offset

0,3

Links

Table of n, a(n) for n=0..9.

C. Defant and K. Zheng, Stack-Sorting with Consecutive-Pattern-Avoiding Stacks, arXiv:2008.12297 [math.CO], 2020.

Example

Sending the permutation 132 through a consecutive-312-avoiding stack results in 231, and a classical 21-avoiding stack then sends 231 to 213, which is not the identity 123. Applying this procedure to any permutation of length 3 other than 132 results in 123, so a(3)=5.

Crossrefs

Cf. A033321, A001006, A337495, A011782, A001405

Sequence in context: A369212 A279553 A007853 * A149952 A337526 A346661

Adjacent sequences: A337519 A337520 A337521 * A337523 A337524 A337525

Keyword

nonn,more

Author

Colin Defant, Aug 30 2020

Status

approved