50467domain: NAppears in sequencesNumber of (2+2)X(n+2) 0..3 arrays with every 3X3 subblock row and diagonal sum equal to 0 3 5 6 or 7 and every 3X3 column and antidiagonal sum not equal to 0 3 5 6 or 7.at n=16A252386Numbers k such that (10^k - 97)/3 is prime.at n=20A293757