3640688640domain: NAppears in sequencesNumber of permutations p of {1,2,...,n} such that p(j) + p(n+1-j) != n+1 for all j.at n=13A155518Sequence a(n) gives the number of ways to seat 2n people around a circular table so that person i does not sit across from person n+i for any 1 <= i <= n.at n=6A167406