2470626domain: NAppears in sequencesNumber of (n+2)X(4+2) 0..3 arrays with no row, column, diagonal or antidiagonal in any 3X3 subblock summing to 0 2 4 5 7 or 9.at n=7A251648a(n) = Product_{p|n, p prime} (1 - p^p).at n=13A307654a(n) = Product_{p|n, p prime} (1 - p^p).at n=27A307654