Number of alternating permutations on 2n letters that avoid a certain pattern of length 4 (see Lewis, 2012, Appendix, for precise definition).
A217810
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) =5a(2) =42a(3) =454a(4) =5680a(5) =78129
External references
- oeis: A217810