250150900354domain: NAppears in sequencesNumber of permutations p of [n] such that the sequence of ascents and descents of 0p or of 0p0 (if n is odd) forms a Dyck path.at n=15A303284Number of permutations p of [2n+1] such that the sequence of ascents and descents of 0p0 forms a Dyck path.at n=7A303286