119836809domain: NAppears in sequencesLet M(k) be the k X k matrix m_(i,j) = i (mod j) - j (mod i); then a(n) = det(M(2*n)).at n=7A075691Number of n X 2 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 0 1 and 1 0 0 vertically.at n=18A207436