21301832domain: NAppears in sequencesNumber of (n+2) X (4+2) 0..3 arrays with every 3 X 3 subblock row and column sum equal to 0 1 3 6 or 7 and every 3X3 diagonal and antidiagonal sum not equal to 0, 1, 3, 6, or 7.at n=20A252188