57323domain: NAppears in sequencesNumber of 2 X 2 matrices having all elements in {0,1,...,n} and determinant in the closed interval [-n,n].at n=24A211031Number of (n+1) X (n+1) -5..5 symmetric matrices with every 2 X 2 subblock having sum zero and one or two distinct values.at n=19A211329