604639domain: NAppears in sequencesNumber of n X n 0..3 matrices whose square is also a 0..3 matrix.at n=3A213985T(n,k)=Number of n X n 0..k matrices whose square is also a 0..k matrix.at n=18A213990Number of 4X4 0..n matrices whose square is also a 0..n matrix.at n=2A213993