287316122domain: NAppears in sequencesThe number of 3-alternating permutations of [n].at n=15A249402Number of permutations p of [n] such that p(i) > p(i+1) iff i == 2 (mod 3).at n=15A249583Number of linear extensions of a poset whose Hasse diagram consists of n binary shrubs with type A_n joins.at n=5A293950