18555136domain: NAppears in sequencesNumber of (n+1)X(n+1) 0..3 arrays with diagonal zero and the i,j-th 2X2 subblock sum equal to the j,i-th 2X2 subblock sum.at n=3A187403T(n,k)=Number of (n+1)X(n+1) 0..k arrays with diagonal zero and the i,j-th 2X2 subblock sum equal to the j,i-th 2X2 subblock sum.at n=18A187408