224610domain: NAppears in sequencesNumber of (n+2)X(2+2) 0..3 arrays with every 3X3 subblock row and column sum 1 3 6 or 8 and every diagonal and antidiagonal sum not 1 3 6 or 8.at n=13A252009Squarefree numbers n such that psi(phi(n)) = phi(psi(n) - n).at n=6A292048