111520domain: NAppears in sequencesNumber of ways to place 2 queens on an n X n chessboard so that they attack each other.at n=40A144945Number of n X 6 0..1 arrays avoiding 0 0 0 and 1 1 1 horizontally and 0 0 1 and 0 1 1 vertically.at n=8A208067Certain directed lattice paths.at n=7A260769