168360domain: NAppears in sequencesNumber of permutations (p1,...,pn) such that 1 <= |pk - k| <= 2 for all k.at n=21A033305a(n) = (n-1)*(2*n-1)*(3*n-1).at n=31A033594Number of permutations of [n] with no fixed points where the maximal displacement of an element equals two.at n=19A321048