204349domain: NAppears in sequencesNumber of (n+2) X (6+2) 0..3 arrays with every 3 X 3 subblock row and diagonal sum equal to 0 3 5 6 or 7 and every 3 X 3 column and antidiagonal sum not equal to 0 3 5 6 or 7.at n=20A252382Approximation of the 3-adic integer exp(3) up to 3^n.at n=12A309900