434542domain: NAppears in sequencesNumber of n X n 0..1 matrices with all row and column sums equal.at n=6A067209T(n,k)=Number of (k*n)Xn binary matrices with all row sums equal and all column sums equal.at n=20A181236T(n,k) is the number of n X n 0..k arrays with row and column sums equal.at n=34A202784