6052530domain: NAppears in sequencesNumber of (n+2)X(4+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000000 00000001 or 00001011.at n=9A260280Squarefree numbers n such that psi(phi(n)) = phi(psi(n) - n).at n=18A292048