Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition).
A217806
Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition).
Terms
- a(0) =1a(1) =4a(2) =28a(3) =260a(4) =2844a(5) =34564a(6) =451868a(7) =6231556a(8) =89510428
External references
- oeis: A217806