406748domain: NAppears in sequencesNumber of (n+1) X (n+1) -3..3 symmetric matrices with every 2 X 2 subblock having sum zero and three distinct values.at n=16A211323Number of length n+1 0..3 arrays with the sum of the squares of adjacent differences multiplied by some arrangement of +-1 equal to zero.at n=8A250272