1548177domain: NAppears in sequencesNumber of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 1000-1110-0111-0001 pattern in any orientation.at n=21A147401Number of -n..n circular arrays x(0..6) of 7 elements with zero sums of x(i) and x(i)*x((i+1) mod 7).at n=16A202009