29676414147domain: NAppears in sequencesNumber of (2+2) X (n+2) 0..3 arrays with every 3 X 3 subblock row and diagonal sum equal to 0 3 5 6 or 8 and every 3 X 3 column and antidiagonal sum not equal to 0 3 5 6 or 8.at n=21A252617