261612domain: NAppears in sequencesLet P be a one-move "rider" with move set M={(1,2)}; a(n) is the number of non-attacking positions of two indistinguishable pieces P on an n X n board.at n=26A222308Number of (n+1) X (6+1) 0..2 arrays colored with the upper median value of each 2 X 2 subblock.at n=13A235952