908138776681domain: NAppears in sequencesNumber of 2 up, 2 down, 2 up, ... permutations of length 2n + 1.at n=9A005981The 2-Up sequence: formed from final entries in rows of A058257.at n=19A0582582 up, 2 down, ..., 2 up, 2 down, 2 up permutations of length 4n+3.at n=4A131454